Latest nightly release

This is a nightly release built from the latest commit. Before you use these builds, make sure to backup your data, especially the save states!

Save states are constantly evolving and are only guaranteed to be compatible on stable (numbered) releases.
The file format may be changed without notice, so be careful when using save states from nightly releases.

You can find the changelog for this build here.

Note

Nightly builds include experimental and in-development features that may not work properly.
When reporting issues, make sure to include the version number (Help > About > Copy version).

Important

It is recommended to install the latest GPU drivers in order to use Direct3D or Vulkan:

• Nvidia: Find your GPU here or use the Nvidia App to update drivers automatically
• AMD: Find your GPU or CPU here or use the download buttons at the top to update drivers automatically
• Intel: Find your GPU or CPU here

Windows users: install the latest Microsoft Visual C++ Redistributable package (x86_64 installer, AArch64/ARM64 installer) before running the emulator. This is mandatory to avoid crashes on startup.

macOS users: follow these instructions to allow Ymir to run on your system. Ymir is signed with an ad-hoc certificate, flagging it as unverified.

Linux users: if you choose to install the Flatpak version, make sure to grant Ymir permission to access the filesystem or your disc images won't load properly.

Ymir v0.3.3

Ymir v0.3.3

Discord | Patreon | Compatibility list | Screenshots

This is a small maintenance release that fixes a regression with Akumajou Dracula X (#904), improves autodetection of the Asia NTSC region (Korea and Taiwan), adds some missing theme colors introduced in recent ImGui updates, and corrects some documentation oversights. It also implements the VDP2 color gradation effect, fixing the background in Saturn Bomberman's Egg Birdon boss fight.

Check the meatier v0.3.2 release notes for details on what's included in this version.

Important

Windows users: install the latest Microsoft Visual C++ Redistributable package (x86_64 installer, AArch64/ARM64 installer) before running the emulator. This is mandatory to avoid crashes on startup.

macOS users: follow these instructions to allow Ymir to run on your system. Ymir is signed with an ad-hoc certificate, flagging it as unverified.

Linux users: if you choose to install the Flatpak version or installed Ymir from the SteamOS's Discover Store, make sure to grant Ymir permission to access the filesystem or your multi-file disc images won't load properly.

VDP2 color gradation

The only notable improvement in this version is the implementation of the VDP2 color gradation effect, which can be seen in the Egg Birdon boss arena of Saturn Bomberman:

Here's a video captured from hardware with a RetroTink 4K of the same scene. Ymir's output perfectly matches what the Saturn produces.

Changes

New features and improvements

• GUI: Specify missing ImGui style colors.
• System: Add Europe PAL and Asia NTSC (in that order) to default preferred regions after North America and Japan.
• VDP2: Implemented color gradation effect. Fixes background in the Egg Birdon boss arena of Saturn Bomberman.

Fixes

• System: Properly autoselect IPL ROMs for Asia NTSC region (South Korea, Taiwan).
• VDP1: Don't automatically mark jumps to 0 as infinite loops. Fixes Akumajou Dracula X no longer booting. (#904)

Which version should I download?

Grab the file matching your operating system and processor architecture:

• windows, linux and macos indicate the operating system
• x86_64 is for Intel or AMD CPUs and AArch64/ARM64 is for ARM CPUs
• All builds are for 64-bit systems

For x86_64 builds, the AVX2 version offers slightly better performance but requires a CPU that supports the instruction set -- pretty much any Intel Core or AMD CPU since 2011 and Intel Pentium/Celeron CPUs from 2020 onwards has support for it. If you don't know if AVX2 is supported or you have no idea what any of this means, it's probably safe to grab the AVX2 version if you don't have an ancient or cheap computer. If it doesn't start up or randomly crashes for no reason, try the SSE2 version.

Every ARM build also includes support for the NEON instruction set.

For Windows releases, you might also need to install the latest Microsoft Visual C++ Redistributable package (x86_64 installer, AArch64/ARM64 installer). Ymir requires Windows 10 or later.

You can also install Ymir on Linux via Flatpak.

The macOS releases work on Apple Silicon (ARM) systems (arm64) and Intel systems (x64). Ymir requires macOS 15 (Sequoia) or later.

FreeBSD users can install Ymir from the Ports Collection:

pkg install Ymir         (uses zenity with GTK3 widgets for SDL3's file dialogs)
pkg install Ymir-gtk4    (uses zenity with GTK4 widgets)

Ymir v0.3.2

Ymir v0.3.2

Discord | Patreon | Compatibility list | Screenshots

This release brings a large set of bug fixes and accuracy improvements once again guided by @celeriyacon's test ROMs, pushing compatibility to just over 94%! A workaround for 16 games described below would bring this number to 94.6%.

The highlight of this version is the huge set of fixes to CD Block HLE, bringing more parity with the LLE counterpart and improving compatibility and stability with dozens of games. VDP1 fixes also resolved a few longstanding issues and brought some games to life.

Performance got another huge boost in multiple avenues with this version. First, thanks to @SternXD, you can now offload audio processing tasks to another CPU core, freeing up the emulator thread to focus more heavily on the SH-2s and general system logic. This alone can boost performance by up to 25% and possibly more, depending on how much work is put on the SCSP DSP.

SH-2 emulation got faster and more accurate by properly emulating the CPU's fetch stage which pulls two instructions in a single fetch, approximately halving the number of expensive memory accesses done by the interpreter. Alongside that, there have been a number of performance microoptimizations to various aspects of SH-2 emulation that combine into another 10-15% boost to emulation of CPU-heavy games. Grandia's FMVs are notoriously intensive, and this set of improvements marks the first time I've seen it run at over 200 fps on my system.

Of course, with every release there's also room for more features. The SH-2 CPUs can now be overclocked up to 500% to reduce lag in poorly-optimized games, or underclocked down to 25% to lower host CPU usage on lighter games. As everything in the Saturn tends to be timing-sensitive, this comes with a disclaimer that it might break games, but it works well in most cases.

There's now support for Japanese characters (visible in the Backup Memory Manager and other places), a number of debugger improvements and new features, new options to hide the game title and performance indicators from the window title bar, an option to pause emulation upon startup, and a few more odds and ends.

Important

Windows users: install the latest Microsoft Visual C++ Redistributable package (x86_64 installer, AArch64/ARM64 installer) before running the emulator. This is mandatory to avoid crashes on startup.

macOS users: follow these instructions to allow Ymir to run on your system. Ymir is signed with an ad-hoc certificate, flagging it as unverified.

Linux users: if you choose to install the Flatpak version or installed Ymir from the SteamOS's Discover Store, make sure to grant Ymir permission to access the filesystem or your multi-file disc images won't load properly.

Compatibility improvements

Here's a small showcase of games that now work on v0.3.2 or had major bugs fixed:

(click any image to zoom)

With v0.3.2, Ymir's compatibility has pushed ahead of Kronos and is just over 94%.

Ymir is becoming a solid competitor. Watch out, Mednafen!

The primary culprit for most of those games are CD Block high-level emulation (the default in Ymir) and VDP1 timing and behavior inaccuracies. To tackle the CD Block problems, Ymir has a new debugger window that lists all CD Block partitions and what buffers are loaded into them:

Within a few minutes of using it, I already caught two bugs! This one in Shellshock, where the same sector was being loaded into the partition multiple times:

And another one in Sonic Jam, which had a sudden jump backwards in the sector read sequence:

Those two bugs alone accounted for the majority of issues encountered with CD Block HLE mode. For example, IRREEL would fail to load level 2 assets. That is now fixed:

Before	After

Not pictured: Completely busted sound | Perfectly pristine sound.

This tool has also helped detect a buffer exhaustion bug that occurred when pausing and unpausing in Panzer Dragoon II Zwei, a Mode 2 Form 2 sector read bug that broke Chisato Moritaka - Watarase Bashi & Lala Sunshine's FMVs, and many more. Here's a list of games that now work correctly with CD Block HLE thanks to those fixes:

• Chisato Moritaka - Watarase Bashi & Lala Sunshine (#604): FMVs now play correctly.
• Chou Jikuu Yousai Macross - Ai Oboete Imasu ka (#605): intro sequence now plays correctly.
• Cyber Speedway (#785): music now resumes properly after pausing and unpausing.
• Digital Dance Mix Vol. 1 - Namie Amuro (#476): animations and songs now play correctly.
• Dragon Force (#866): Working Designs logo FMV now plays correctly.
• Gunbird (#625): boss animations now play correctly.
• Legend of K-1 - The Best Collection (#758): FMV of third fight now plays correctly.
• LifeScape - Seimei 40 Okunen Haruka na Tabi (#598): no longer freezes on opening FMV.
• Mahjong Yon Shimai - Wakakusa Monogatari (#527): no longer freezes on character select screen.
• Marvel vs. Street Fighter (#667): no longer crashes on Capcom logo.
• Mass Destruction (#664): intro FMVs now play at full speed and in-game music now plays.
• NiGHTS Into Dreams... (#437): Trick Ribbon music plays correctly at all times.
• Panzer Dragoon II Zwei: no longer softlocks after pausing and unpausing multiple times.
• Senken Kigyouden / Xianjian Qixiazhuan (#409): graphics now load correctly.
• Shellshock (#344): no longer crashes on CORE logo.
• Shining Force III (#712, #771): no longer gets stuck on Yes/No dialog choices or crash with CD read errors.
• Sonic Jam (#83): in-game music now plays correctly.
• Tilt! (#872): intro FMVs now play at full speed.
• X-men vs. Street Fighter (#667): no longer crashes on Capcom logo.
• and probably more!

SH-2, VDP1 and VDP2 fixes also improved compatibility with:

• Dark Savior (#134): sprites are no longer spliced across frames.
• Deep Fear (#779): color palette no longer messes up when opening the inventory.
• Magical Night Dreams - Cotton 2 (#728): character highlight effect is now fixed.
• Neon Genesis Evangelion - Koutetsu no Girlfriend (#581): now plays FMVs.
• Nobunaga no Yabou Returns (#596): now plays FMVs and goes in-game.
• Revolution X - Music Is the Weapon (Europe): title screen now displays the band.
• Ryuuteki Gosennen - Dragons of China (#856): text frames are no longer shifted to the right.
• Scorcher (#281): game no longer crashes immediately in Training mode or randomly in other modes.
• Shellshock (#344): in-game terrain is now drawn at full width (half resolution).
• Shining the Holy Ark (#287): game speed is correct, no longer double-taps movements.
• Stellar Assault (#844): stopped booting on 0.3.1 due to a VDP1 infinite loop detection optimization. This is now fixed.

Dark Savior, notably, has had the sprite splicing bug for a long time (#134) that affected the intro sequence and nearly all gameplay scenes. In v0.3.2, this bug was fixed by an SH2 accuracy improvement guided by @celeriyacon's tests.

Before	After

The deinterlace effect received some adjustments to fill in gaps between sprites on high resolution modes, affecting games such as Sonic Jam (#853) and Astra Superstars (#784).

Threaded VDP1 rendering caused some problems with several games (#898). This release fixes most of the issues, though there are still a few remaining glitches to fix:

• BlackFire (#790): GUI ...

Ymir v0.3.1

Ymir v0.3.1

Discord | Patreon | Compatibility list

This release adds many performance optimizations to the VDP2 renderer, bringing up to 40% more performance on graphics-heavy games. Users have reported running Virtua Fighter 2 and Last Bronx at full speed on an i7-2600K and many cases of lower-powered CPUs are now capable of running Ymir with less stuttering. In my tests, it consistently runs faster than Mednafen, Kronos and Yaba Sanshiro in high-profile games and a few obscure ones too.

This version also includes a few more graphics rendering fixes, more SH-2 emulation accuracy improvements (thanks to @celeriyacon once again), and some adjustments to the CUE sheet parser to fix some CD audio track misalignments (including some ImgBurn dumps).

Important

Windows users: install the latest Microsoft Visual C++ Redistributable package (x86_64 installer, AArch64/ARM64 installer) before running the emulator. This is mandatory to avoid crashes on startup.

macOS users: follow these instructions to allow Ymir to run on your system. Ymir is signed with an ad-hoc certificate, flagging it as unverified.

Linux users: if you choose to install the Flatpak version or installed Ymir from the SteamOS's Discover Store, make sure to grant Ymir permission to access the filesystem or your multi-file disc images won't load properly.

Changes

New features and improvements

• Debugger: Add Priority Stack to VDP2 debug overlay.
• VDP2: Various performance optimizations to the software renderer, improving performance in graphics-bound games (especially in high resolution modes). Technical details:
  • RBG1 was being unnecessarily rendered when NBG0 was enabled and RBG1 was disabled
  • Remove redundant transparency bit since priority zero acts as transparency
  • Remove various unused function arguments, reducing CPU register and stack pressure
  • Pass down VDP2 register references as arguments rather than fetching them from scratch everywhere
  • Reuse line data (i.e. skip recomputing lines) when rendering vertical mosaic
  • Bit-pack character pattern data in a single 32-bit value
  • Microoptimize scroll coordinates calculations
  • Rotation parameter table calculations:
    • Specialize calculations for (1) no coefficient table, (2) per-line coefficient table and (3) per-dot coefficient table
    • Hoist coefficient table enable and per-dot coefficients checks out of the loop
    • Make the inner loops SIMD-friendly
    • Avoid unnecessary computation of transparency and line color screen data if they are disabled
  • Microoptimizations to the compositor function:
    • Layer sorting now uses a combined key
    • Gather layer data in one single loop
    • Pixel fetching is now templatized and some bail out checks are done earlier
    • Color offset calculation enable flag is cleared in the fetch loop if no offset is actually applied

Fixes

• Debugger: Various SH2 stack analysis fixes.
• Game DB: Add slow VDP1 flag to Funky Fantasy to fix slow FMVs.
• Media: Detect postgaps in data tracks when the CUE sheet doesn't explicitly announce them. Fixes audio track shifts in bad Virtua Fighter 2 dumps.
• Media: Fix PREGAP/POSTGAP handling in CUE/BIN dumps. Fixes shifted audio tracks in games dumped with ImgBurn.
• SH2: Fix illegal slot instruction exception handling. (thanks to @celeriyacon)
• VDP1: Add game-specific flag for skipping command processing if the top of the table is empty. Enable it exclusively for Sekai no Shasou kara - I Swiss-hen - Alps Tozantetsudou no Tabi. Fixes missing graphics in Gungriffon. (#810)
• VDP1: Disable early polygon drawing termination when rendering polygons when user clipping mode is inverted. Fixes clipped polygons around the minimap in Machine Head (#767).
• VDP1: Implement simple infinite loop detection. Fixes slowdown in the Mojave Desert stage (1-2) in Gale Racer.
• VDP2: Apply color calculations to transparent sprite mesh on layer 0. Fixes stripes on ground plane in Gungriffon.
• VDP2: Apply color offset to transparent sprite mesh on layer 0 in a separate step. Fixes missing spotlight in the Colonel battle in Mega Man X4. (#818)
• VDP2: Fix VRAM access calculations when RBG1 is enabled. Fix missing car graphics regression in Gale Racer. (#359)
• VDP2: Fix and use line color screen calculation ratio when LNCL is inserted. Fixes text background issues in Doukoku Soshite. (#502)

Which version should I download?

Grab the file matching your operating system and processor architecture:

• windows, linux and macos indicate the operating system
• x86_64 is for Intel or AMD CPUs and AArch64/ARM64 is for ARM CPUs
• All builds are for 64-bit systems

For x86_64 builds, the AVX2 version offers slightly better performance but requires a CPU that supports the instruction set -- pretty much any Intel Core or AMD CPU since 2011 and Intel Pentium/Celeron CPUs from 2020 onwards has support for it. If you don't know if AVX2 is supported or you have no idea what any of this means, it's probably safe to grab the AVX2 version if you don't have an ancient or cheap computer. If it doesn't start up or randomly crashes for no reason, try the SSE2 version.

Every ARM build also includes support for the NEON instruction set.

For Windows releases, you might also need to install the latest Microsoft Visual C++ Redistributable package (x86_64 installer, AArch64/ARM64 installer). Ymir requires Windows 10 or later.

You can also install Ymir on Linux via Flatpak.

The macOS releases work on Apple Silicon (ARM) systems (arm64) and Intel systems (x64). Ymir requires macOS 15 (Sequoia) or later.

FreeBSD users can install Ymir from the Ports Collection:

pkg install Ymir         (uses zenity with GTK3 widgets for SDL3's file dialogs)
pkg install Ymir-gtk4    (uses zenity with GTK4 widgets)

Ymir v0.3.0

Ymir v0.3.0

Discord | Patreon | Compatibility list

The first big release since my first "vacation" of sorts includes a sizable amount of bug fixes, compatibility improvements, more accurate emulation (thanks again to @celeriyacon) and some new features to play with.

First, two new peripherals have been added: the Shuttle Mouse and the Virtua Gun. However, you will note that 0.3.0 only includes the mouse peripheral. This is because the Virtua Gun has lots of issues and is only usable with a single game: House of the Dead. Download a nightly build if you want to try it out.

Save states also got some love. Have you accidentally saved a bad state on top of a good one? Push the Undo Save State button to get the old state back. Do you regret loading a state? Use the Undo Load State to go right back where you were just before loading it. Ymir now stores one additional save state per slot and one load state globally for this feature.

The SH2 debugger received many usability improvements this version with the addition of the Data Stack and Call Stack views, a navigable viewport, and enable/disable toggles for breakpoints and watchpoints.

And, of course, this version comes with plenty of bug fixes mostly focusing graphics as you've come to expect.

Important

Windows users: install the latest Microsoft Visual C++ Redistributable package (x86_64 installer, AArch64/ARM64 installer) before running the emulator. This is mandatory to avoid crashes on startup.

macOS users: follow these instructions to allow Ymir to run on your system. Ymir is signed with an ad-hoc certificate, flagging it as unverified.

Linux users: if you choose to install the Flatpak version or installed Ymir from the SteamOS's Discover Store, make sure to grant Ymir permission to access the filesystem or your multi-file disc images won't load properly.

Compatibility improvements

As usual, plenty of graphics rendering issues have been fixed, many of which have been detected by diligent work from the testers. Thanks!

A notable improvement made in this version is the VDP1 cycle counting method rework. It is still a rough approximation and still results in a much faster VDP1 than the real Saturn's, but is much less prone to stability problems. This change has fixed crashes, freezes, performance issues and graphics glitches in many games, including:

• Beach de Riichi
• Burning Rangers
• DonPachi
• Dungeons & Dragons Collection
• Isto E Zico - Zico no Kangaeru Soccer
• Real Bout Garou Densetsu Special
• Road Rash
• Virtua Cop

A number of game-specific flags have been added to the emulator core to work around extremely finicky bugs without affecting already working games. Here's a list of games that are now playable thanks to these flags:

• Vampire Savior - The Lord of Vampire
• Baku Baku Animal - World Zookeeper Contest (European version)
• Chisato Moritaka - Watarase Bashi & Lala Sunshine
• Deep Fear
• Dragon Ball Z - Idainaru Dragon Ball Densetsu
• Jikkyou Oshaberi Parodius
• Metal Fighter Miku

These flags also help fix graphics issues in a few more games:

• Emit Vol. 3 - Watashi ni Sayonara o
• Fishing Koushien II
• Spot Goes to Hollywood (European version only)
• Steamgear Mash
• Waku Waku 7

With that, compatibility stands at just over 92%, on par with Kronos.

New peripherals: Shuttle Mouse and Virtua Gun

Important

The Virtua Gun is EXPERIMENTAL and is only available in development and nightly builds.
It only works more or less properly with House of the Dead and has issues with pretty much every other game that supports it. See #787 for a list of issues. For this reason, the peripheral is disabled in 0.3.0, but you can try it out on the nightly builds.

In 0.3.0 you can use a Shuttle Mouse with games that support it.

Virtua Cop 2 plays great with the mouse!... if you can deal with a two-frame input delay.

Also, in nightly builds only, you can select the Virtua Gun. However, as noted above, it currently only works reasonably well with House of the Dead. It has worse latency than the Shuttle Mouse though, so temper your expectations.

The new Mouse Capture Mode setting allows you to control how the mouse capture works for the gun:

• System cursor: in this mode, the light gun reticle follows your system mouse cursor. This works well in cases where you only want to use a single Virtua Gun.
• Physical mouse: in this mode, each physical mouse attached to the computer can be bound to a different Virtua Gun. Yes, you can have two or more mice connected to the same PC and, yes, they are independent of one another.

The warning is also displayed in the Input settings window.

You can customize the reticle to your heart's content.

crosshairs.mp4

There's an infinite number of combinations!

Build fixes

The Windows SSE2 build now correctly targets the SSE2 instruction set, which should make 0.3.0 compatible with old CPUs once again.

The macOS ARM executable is now signed with an ad-hoc signature to work around the "damaged app" error. You still have to allow execution of an "untrusted" application, but at least this no longer blocks you from running the emulator altogether. Also, macOS builds no longer include two copies of the executable, roughly halving their size.

UI improvements

Every save state slot now holds an additional undo entry, which you can recover in case you accidentally saved a state. You can restore it with the new "Undo save state" action. Similarly, if you accidentally loaded a save state, you can go back to the previous state with the "Undo load state" action.

Each save state slot tells you if you have an undo for it.

New options have been added to manage full screen mode. You can now select a display and a resolution, including borderless windowed and exclusive full screen modes.

There's also a new option to select the graphics backend from Direct3D 11, Direct3D 12, Vulkan, Metal or OpenGL. This is in preparation for GPU rendering, which is still a work-in-progress. GPU rendering was slated to land on this version, but I decided to postpone it to fix some serious stability and performance issues that occur with higher internal resolution scaling ratios. For sneak peeks, check #60.

Debugger

The SH2 debugger received many usability and utility upgrades this version. The first thing you'll notice are the new Data Stack and Code Stack sections below the registers listing the contents of the stack and the call site return addresses respectively. These require debug tracing to be enabled (F11) to trace code execution and can be hidden from the new Stack menu in the debugger window.

The disassembly view can now be freely scrolled and navigated with both keyboard and mouse:

• Up/down arrow keys: move cursor up/down one instruction.
• Page up/down: move cursor up/down one page.
• Home/end: move cursor to the top/bottom of the viewport.
• The cursor is kept below 15% of the top and above 35% of the bottom of the viewport.
• Scroll with the mouse wheel to move the viewport.

The cursor is represented by a green line and you can use the keyboard shortcut F9 to toggle a breakpoint on that address and Shift+F9 to enable/disable an existing breakpoint. Yes, now you can disable breakpoints and watchpoints without removing them from the list. Also, their performance cost has been drastically reduced.

Note the hollow circles. Those breakpoints are disabled - they won't be hit, but they are kept in the list in case you need them again.

The VRAM access patterns are now color-coded in the VDP2 VRAM access delay view. Red CPs indicate illegal access timings based on the corresponding NBG parameters (and PN accesses for scroll NBGs).

It doesn't explain why, but these two CP0 accesses are not good.

The window also has a **Generate test case...

v0.2.1

Ymir v0.2.1

Discord | Patreon | Compatibility list

This patch fixes a couple of issues with the update checker, a rare crash involving the rewind buffer, and comes with the usual set of graphics bug squashing. It also includes improvements from a new contributor, @mmkzer0, and a significant change to VDP1 rendering that fixes a long-standing issue with threaded rendering.

As noted in the previous version, future updates (such as this one) will not be as substantial as previous ones as I'm splitting my time with other activities.

Caution

The Windows SSE2 build is currently targeting the SSE4.2 instruction set due to a mistake in the build system configuration, resulting in crashes on old CPUs. Also, the macOS ARM build is incorrectly flagged as "damaged". A fix will be available in version 0.3.0. The latest nightly also includes a fix. See #713 and #698.

Caution

Due to a programming oversight, the application will crash if automatic update checks are enabled and the nightly build is broken. To avoid this, either update to the latest nightly (if available) or disable automatic update checks. If Ymir is crashing, edit Ymir.toml with a text editor and change CheckForUpdates from true to false.
This will be fixed in the next release.

Important

Windows users: install the latest Microsoft Visual C++ Redistributable package (x86_64 installer, AArch64/ARM64 installer) before running the emulator. This is mandatory to avoid crashes on startup.

macOS users: follow these instructions to allow Ymir to run on your system. Ymir is signed with an ad-hoc certificate, flagging it as unverified.

Linux users: if you choose to install the Flatpak version, make sure to grant Ymir permission to access the filesystem or your disc images won't load properly.

Improved threaded VDP1 rendering

The old threaded VDP1 rendering interfered with VDP1 timings and caused issues in a few games (#233). With the new design, this is no longer the case - the VDP1 logic and timings are still driven by the emulator thread, but the drawing itself can be moved to a dedicated thread (or a GPU renderer, eventually). This option is now enabled by default as it brings up to 30% performance boost depending on how VDP1-heavy the game is. The old "Include VDP1 rendering in VDP2 renderer thread" option was removed to make way for this implementation.

UI improvements

Save states menus have been split into Load and Save sections to avoid confusion and simplify interactions. Selecting a save state from either menu will also switch the currently selected slot for quick load/save.

The Backup Memory Manager was moved from the File to the System menu, to bring it closer to other system-related actions such as managing cartridges.

Debugger

The memory viewers now have a button to dump the contents of an entire memory region to a file. This can be useful to compare against other emulators or for offline research, disassembly, and more. These dumps are saved to <profile>/dumps/<game code>-<region name>-<base address>-<size in bytes>.bin.

The VDP2 VRAM access delay window now shows the access shift introduced by misaligned timings for a given background layer's character or bitmap data which affects World Heroes Perfect's intro sequence. It's the same issue that causes the full screen pictures in Capcom Generation - Dai-5-shuu Kakutouka-tachi's art gallery to be split.

Changes

New features and improvements

• App: Added "Take Screenshot" action to File menu.
• App: Moved "Backup Memory Manager" action from File to System menu.
• Debugger: Added Dump memory region button to the Memory Viewer to dump the currently selected region to a raw .bin file in the profile’s dump path. (#678; @mmkzer0)
• Debugger: Display VRAM data access shifts separately from CP delays in the VDP2 VRAM access delay window and display them for scroll BGs as well.
• Rewind: Reset rewind buffer on hard resets and whenever the CD Block LLE settings is changed.
• Save states: Separated save states menu into Load and Save to avoid confusion and simplify interactions.
• Updater: Added compile-time flag Ymir_ENABLE_UPDATE_CHECKS to enable or disable the automatic update checker, including the onboarding process.
• VDP1: Reworked renderer code structure. Allows threading without affecting timings and paves way for other rendering backends. (#233)

Fixes

• Settings: Properly reload binds for "increase/decrease speed by 25%".
• Updater: Create state/updates folder before writing .onboarded file in case the user opts out of automatic update checks. Fixes update check onboarding popup always appearing on startup. (#708)
• Updater: Detect nightly -> stable update when the current version matches the stable version.
• VDP1: Reduce VBlank erase timing penalty to fix graphics artifacts in Battle Garegga's options menu. (#649)
• VDP2: Allow bitmap data access during SH-2 cycles. Fixes FMV flickering in Lunar - Silver Star Story, Shin Kaitei Gunkan, and Mechanical Violator Hakaider (#438, #446, #658)
• VDP2: Apply VRAM bank data access shift to scroll BGs. Fixes shifted borders in World Heroes Perfect's demo sequence. (#643)
• VDP2: Disable VRAM access restrictions based on ZMCTL parameters. Fixes missing background graphics in Baku Baku Animal - World Zookeeper. (#646)

Which version should I download?

Grab the file matching your operating system and processor architecture:

• windows, linux and macos indicate the operating system
• x86_64 is for Intel or AMD CPUs and AArch64/ARM64 is for ARM CPUs
• All builds are for 64-bit systems

For x86_64 builds, the AVX2 version offers slightly better performance but requires a CPU that supports the instruction set -- pretty much any Intel Core or AMD CPU since 2011 and Intel Pentium/Celeron CPUs from 2020 onwards has support for it. If you don't know if AVX2 is supported or you have no idea what any of this means, it's probably safe to grab the AVX2 version if you don't have an ancient or cheap computer. If it doesn't start up or randomly crashes for no reason, try the SSE2 version.

Every ARM build also includes support for the NEON instruction set.

For Windows releases, you might also need to install the latest Microsoft Visual C++ Redistributable package (x86_64 installer, AArch64/ARM64 installer). Ymir requires Windows 10 or later.

You can also install Ymir on Linux via Flatpak.

The macOS releases work on Apple Silicon (ARM) systems (arm64) and Intel systems (x64). Ymir requires macOS 15 (Sequoia) or later.

FreeBSD users can install Ymir from the Ports Collection:

pkg install Ymir         (uses zenity with GTK3 widgets for SDL3's file dialogs)
pkg install Ymir-gtk4    (uses zenity with GTK4 widgets)

v0.2.0

Ymir v0.2.0

Discord | Patreon | Compatibility list

This update introduces low-level CD Block emulation, an optional major feature that significantly improves accuracy. Additionally, this release features a simple automatic update check that you can opt-in, SH-2, M68000 and SCU DMA timing accuracy improvements and a handful of the usual bug fixes.

The build system has been upgraded to support more complex libraries such as curl and OpenSSL. These libraries enable implementation of HTTP web requests, which allows Ymir to check for updates directly from GitHub releases (like the one you're reading right now). Because of these changes, the macOS build has been split into x86_64 and ARM64 builds instead of an universal package.

This version also fixes a known issue in version 0.1.8 related to the rewind buffer.

The CD Block LLE changes have not introduced any breaking changes to the save state file structure -- 0.2.0 is still compatible with 0.1.x save states.

Important

CD Block LLE mode fundamentally changes how CD Block emulation works. For that reason, enabling and disabling the option forces a hard reset as it is near impossible to reconciliate the HLE and LLE states.

Save states created in LLE mode require the user to have the CD Block ROM used to originally create the state in order to load it. Save states created in HLE mode require no extra ROM. Loading a save state will automatically adjust the CD Block LLE mode accordingly and attempt to load the matching ROM if available. If the ROM cannot be found, the save state will not be loaded.

Caution

The Windows SSE2 build is currently targeting the SSE4.2 instruction set due to a mistake in the build system configuration, resulting in crashes on old CPUs. Also, the macOS ARM build is incorrectly flagged as "damaged". A fix will be available in version 0.3.0. The latest nightly also includes a fix. See #713 and #698.

Important

Windows users: install the latest Microsoft Visual C++ Redistributable package (x86_64 installer, AArch64/ARM64 installer) before running the emulator. This is mandatory to avoid crashes on startup.

macOS users: follow these instructions to allow Ymir to run on your system. Ymir is signed with an ad-hoc certificate, flagging it as unverified.

Linux users: if you choose to install the Flatpak version, make sure to grant Ymir permission to access the filesystem or your disc images won't load properly.

Starting from this version, expect the next updates to come a bit slower and/or with less bullet points in the changes list, as I'm going to divide my attention with other projects.

Compatibility improvements

Here's a small showcase of games that now work on 0.2.0 or had major bugs fixed:

(click any image to zoom)

Thanks to the community, the compatibility list is now completely filled. Ymir now boasts over 90% compatibility over the whole collection of Saturn games with the majority of games working flawlessly or with minor issues. Some configuration tweaks are required in order to maximize compatibility -- you can find instructions in the Additional notes column of the spreadsheet.

There are three major factors that significantly improved compatibility from 0.1.x:

• The newly introduced low-level CD Block emulation option
• Improved SH-2 and M68EC000 bus timings
• SCU DMA, SCU DSP DMA and SH-2 DMAC timing and bus stalls

The low-level CD Block emulation mode requires a valid CD Block ROM to work. When enabled, it greatly improves emulation accuracy of the CD drive and the commands sent by games. From my own notes and community testing, at least 23 games are now capable of going in-game or have major issues fixed when this option is enabled. A few games present issues when the option is enabled, including Grandia, Mahjong Hyper Reaction R and LifeScape - Seimei 40 Okunen Haruka na Tabi.

You will need to procure these ROMs on your own.

The timing improvements made to SH-2 and M68EC000 bus exchanges fixed a problem where Resident Evil would get stuck in scripted sequences, leaving characters bobbing their heads in silence forever. This change also slightly boosts overall performance as the CPUs are now running a few less instructions per frame.

Finally, the DMA timings and bus stalls were a requirement for CD Block LLE to work. The CD block subsystem requires very tight timings for each data transfer done between the CD drive, the SH-1 CPU embedded in the block and the rest of the system, and the method used previously by Ymir (run full DMA transfers instantly) was incompatible with this model. Now, Ymir will perform transfers one by one, as many as can fit within a cycle budget, and stall components (effectively skip processing them) if the bus signals that the transfer must wait. The good thing is that this method also improves compatibility with more than 20 games even with CD Block LLE is not used.

Low-level CD Block emulation reduces performance by about 15-20% due to emulating an additional CPU -- the SH-1 runs at 20 MHz, not too far from the 28 MHz of the two main SH-2 CPUs. The old high-level emulation mode will not be replaced by this option because it provides better performance and flexibility. For example, you cannot change the read speed on the LLE version because the CD Block program expects disc sector transfers to happen at very precise intervals. Any slight deviation in these timings is seen as an "error" by the program, and the block starts reporting disc read failures to the Saturn, resulting in non-working games.

The CUE parser has received an overhaul which should hopefully fix almost all audio track shifting issues. Additionally, Ymir will now correctly load cue sheets that reference .wav files as long as the files are in 44100 Hz, stereo, 16-bit raw PCM format (which exactly matches CD audio data). The CHD and ISO loaders received small fixes to improve compatibility with non-Redump dumps.

Rounding up the list is a small number of VDP1 and VDP2 fixes which deal with minor graphics issues found in a number of games as you've come to expect. Also, there's a new 6 MiB development DRAM cart option required by the Heart of Darkness prototype. Finally, a small SMPC change allows the dev kit BIOS to play its animation, but it still doesn't go past the Saturn logo.

Automatic update checks

A new automatic update check system has been introduced to help you know when Ymir has a new version. When you first launch Ymir, you will be greeted with an onboarding dialog:

When a new version is made available, be it a stable or a nightly version, Ymir will display a popup window with links to the release notes and a direct download link to the new version. On a future version, this process will be fully automated.

New options have been added to Settings > General to configure the update checker. Here you can also open the release notes and grab the binary package for the stable and nightly releases.

You can also check for updates from the Help menu:

Debugger

The old CD Block command trace has received a small upgrade: the commands and responses are now color-coded by the command type and status, respectively.

New debug windows have been added to trace the LLE CD drive communications as well as commands and responses.

A couple of new VDP2 debugger windows have been added: a CRAM palette viewer and a display overlay with various customizable views. The overlay display allows you to see which layers are being rendered, window states for every layer, RBG0 rotation parameters being displayed, and whether color calculations or shadows are in use. More overlays will come in the future.

<img width="1227" height="972" alt="image" src="https://github.com/user-attachments/assets/2fa4...

v0.1.8

Ymir v0.1.8

Discord | Patreon | Compatibility list

This releases focuses heavily on bug fixes, with a touch of quality-of-life features, debugging tools, and small but welcome improvements across the board. There are no major improvements or new features this time.

Official ARM Windows and FreeBSD builds have arrived, thanks to @tordona and @bsdcode respectively. You can find the Windows version attached in this release and the FreeBSD version in the ports collection.

This is probably the last 0.1.x release as I'm planning to rewrite CD Block and SMPC emulation for next version, which will be labeled 0.2.0. These components have been the Achilles's heel of Ymir's emulation accuracy, causing a large number of hard issues to investigate and solve. For this reason, expect the next release to take a bit longer or be less substantial that these last releases. Also, there's a small but non-negligible chance that the components will have big enough changes that save state compatibility with 0.1.x might be broken. I'll try my best to avoid this, but compatibility and accuracy will take precedence over convenience if necessary.

Compatibility improvements

Here's a small showcase of games that now work on 0.1.8 or had major bugs fixed:

(click any image to zoom)

Thanks to the enormous efforts of @GoodWall533, @thelastangryman1907 and jabeck1 (and, of course, everyone else that has contributed), the compatibility list has reached over 50% of total games reported with about 85% compatibility. Filing compatibility reports is a great way to help the community too, so don't hesitate to test games and write your reports here!

Let's start with the elephants in the room: the CD Block and the SMPC, both of which now have test ROMs built by @celeriyacon. These two components have shown the worst cracks of Ymir's emulation -- every single SMPC test fails, and out of the two CD Block tests available, it only barely manages to pass one. My attempts to fix the components to pass the tests have resulted in worsened compatibility, so they will remain failing for the time being for the sake of compatibility. Both are responsible for a large number of freezes, crashes, no-boots and similar issues, and will require significant rework to be fixed. For that reason, I have decided to shift the focus onto low-hanging fruits this version and leave these components in their just barely working states until next version.

Not looking great here, but sometimes we have to take a step backward before we can take two steps forward.

That's not to say they haven't received any fixes, though. The test ROM has helped iron out some kinks with CD Block emulation, enough to get Virtual On - Cyber Troopers to not immediately crash after winning a fight (although it's still not fully stable either), and the SMPC tests have helped fix input problems with both the JP and EU releases of Discworld. Also, the CHD loader has received enough fixes to allow every Last Bronx dump I tested to boot properly, and the CUE parser has been rewritten, fixing dozens of issues with misaligned audio tracks and problems loading files with Unicode characters. The application now supports UTF-8 characters everywhere, although the fonts won't display all characters properly yet (Japanese text, most notably).

The internal game database has been upgraded to allow detecting games that benefit (but not require) the Backup RAM cartridge. Ymir will automatically insert the cartridge for these games:

• Dezaemon 2 -- required for saving games
• Sega Ages - Galaxy Force II -- required for saving replays

These cartridges will have unique names based on the game name and are saved to <profile>/backup/games/bup-ext-<title> [<code>].bin.

The SH-2 also got a few small fixes to edge cases thanks to new tests in @celeriyacon's SH-2 test ROM.

The SCU only had two fixes, one of which was affecting Phantasy Star IV in the Sega Ages collection from properly loading its graphics. Speaking of the games, there have been more SCSP fixes than usual this time which also helped improve compatibility with all games on the Phantasy Star collection. All of the games can now be played properly, although no one has played them to completion on Ymir yet. The SCSP fixes have also solved many problems such as soundtracks playing on only one channel, sound effects missing in multiple games, ear-bursting static noises, among others. Notably, CroNSF (also from @celeriyacon) is now playing songs properly!

Pairs of opposite sawtooth waves are used to simulate pulse waves of any width. Clever.

Finally, let's talk about graphics. Just like previous releases, there have been a multitude of VDP1 and VDP2 fixes, but this time, Ymir's VDP1 renderer has been upgraded to be pixel-perfect thanks Lordus (of DraStic fame). The new renderer received multiple optimizations and upgrades, including cycle-counting the VBlank erase process which fixes the flickering subtitles in Panzer Dragoon's FMVs (and fixes hangs in Parodius for some unexplainable reason), reworked erase and swap timings which fixes many cases of flickering or missing graphics, and a rough estimate-based cycle counting method for commands that solves significant slowdowns seen in Baroque's FMVs.

A VDP1 hack introduced on 0.1.7 to fix Mega Man X3's sprites has been reverted as it was causing problems on multiple games. This means the game's sprites are once again broken, but the upside is that at least 9 other games no longer have flashing or missing sprites.

As for the VDP2, yet another of @celeriyacon's test ROMs has helped tighten and improve video signal timings. Ymir was using an approximation that didn't quite yield the exact NTSC and PAL frame rates. Now, both modes target exactly 59.97 and 50 Hz respectively with very accurate VBlank and HBlank timings as well as VCNT sequences. Exclusive monitor modes (which no games seem to use) are partially working.

RBG rendering accuracy fixes have solved a longstanding problem in Radiant Silvergun's Stage 2C:

This used to be janky. Not anymore.

You can find the rest of the fixes in the Changes section below.

UI improvements

Ymir will now report slightly more useful error messages when it is unable to load a disc image which should help pinpoint the problem, be it a missing .bin file, a syntax error in a .cue file, a corrupted .chd, or anything of the sort. Also on the topic of errors, if the application fails to launch for some reason (such as failing to initialize the audio or video subsystems), it will display a message box with a short message describing the problem -- much better than the application not launching at all and leaving everyone (including me) confused. Also, thanks to @Wunkolo, macOS now has a global exception handler for serious issues like the one made available for Windows and Linux on 0.1.7.

The application is now capable of loading SDL game controller databases and includes a community-sourced database with the package, which should help improve compatibility with a variety of controllers.

On Windows 11, the window corners are now square rather than rounded.

An error box will be displayed if you attempt to load a game that requires a ROM cartridge (Ultraman - Hikari no Kyojin Densetsu and The King of Fighters '95) for which you don't have the image file in <profile>/roms/cart:

The CD Block section in the System State window will now display the file being currently read, if available -- a feature requested by game translators.

Debugger

In order to help troubleshoot some of these bugs, new debugging tools have been developed which may also be useful to homebrew developers.

You can now add watchpoints to both SH-2 debuggers. Watchpoints suspend execution when a particular memory address is read or written -- extremely useful to find out what is changing or accessing a particular value (especially hardware registers), as long as it's done by an SH-2 instruction.

The SCSP has gained its first set of debugging tools:

• A slots viewer, showing the state of all registers as well as an oscilloscope of the output of each slot
• An oscilloscope with the final output sent to the speakers
• A simple KYONEX event trace (which will be improved in the future)

There's a new window that displays some of the most important VDP2 layer...

v0.1.7

Ymir v0.1.7

Discord | Patreon | Compatibility list

This version brings the customary set of bug fixes along with a bunch of new features, including support for the Arcade Racer and Mission Stick peripherals (in both three- and six-axis modes), the ability to take raw screenshots, new video options to improve frame pacing in windowed mode and make better use of high refresh rates when synchronizing video, a global exception handler to catch unexpected emulator crashes, and even the debugger got some attention this time - the SH-2 debugger is finally actually useful and has been an invaluable asset to help investigate and troubleshoot many bugs!

This version also brings overall performance improvements by using OS-specific features for manual reset events (used to synchronize the GUI, emulator and VDP renderer threads) as well as improving SH-2 SLEEP instruction handling. The performance uplift varies a lot between games and systems, with some seeing as much as 10% more performance.

Thanks to @Wunkolo, macOS builds are now universal, supporting both Apple Silicon and Intel-based systems in one binary. @bsdcode has been adding support for FreeBSD builds as well (#385, #389, #421), which is now available in the FreeBSD Ports Collection here.

Nightly builds are now available here. Keep in mind these are not as thoroughly tested and may contain bugs, but they're very useful for testers who wish to contribute to the evolution of Ymir or users who want to stay on the bleeding edge.

Important

Save state files created by any stable release are guaranteed to be forwards-compatible with any future version of Ymir, both stable and nightly. Save state files created by nightlies have no such guarantee. Save state files are not backwards-compatible.

Compatibility improvements

Here's a small showcase of games that now work on 0.1.7 or had major bugs fixed:

(click any image to zoom)

Thanks to the issue reports from many testers and users, Ymir has received numerous improvements and bug fixes. New testers have joined the community, with special mention to @thelastangryman1907 who has reported dozens of bugs for many obscure Japanese games. Of course, I should also mention long-time testers who have been helping ensure Ymir doesn't have any regressions: @Zet-sensei, @celeriyacon, @AydanWatkins, @GoodWall533, @Silanda, @waspennator, @Immersion95, @markkrauth, and many others. Sorry if I forgot someone, the list just keeps growing!

The compatibility list now has more than 10% of total games reported with nearly 80% compatibility. Filing compatibility reports is a great way to help the community too, so don't hesitate to test games and write your reports here!

Moving on to specific fixes, let's start with the brains of the Saturn: the SH-2s. The improvements in cache emulation accuracy in 0.1.6 have been deemed stable enough to be considered safe to use when needed. As such, Ymir's internal game database has been updated to force-enable this feature for Astal, Dark Savior, and Soviet Strike, as these games are known to have compatibility issues without cache emulation.

Some fixes to SH-2 interrupt handling (particularly DMAC and FRT) have finally solved a long-standing stability issue in Daytona USA (#209) and allowed Shellshock to boot up (#344) (although Shellshock requires boosted CD Block read speeds to avoid a crash on the intro FMV). The SLEEP instruction has also been fixed and sleep/standby modes are now implemented, allowing the emulator to efficiently skip processing the CPU if it's in one of those modes as well as wake them up when an interrupt is signaled. This allows Culdcept to boot (#346) and improves performance of games that make use of the instruction.

Speaking of non-booting games, a good number of these problems were caused by CD Block or image loading issues. Last Bronx is a good example -- it uses two data tracks: a Mode 1 track containing the game's code and data, and a Mode 2 track with compressed data in a proprietary format. The way these tracks are laid out is unusual - the second data track has a pregap that wasn't being handled correctly by Ymir. Now, most Last Bronx dumps work correctly (#238), but some CHD dumps are still causing problems.

The newly-implemented support for CD-ROM Mode 2 tracks has also fixed the missing intro FMV in NiGHTS into Dreams, a really old bug reported by yours truly before releasing 0.1.0 (#46). Additional improvements to BIN+CUE and CHD loading have allowed other games to boot or fix their audio desync issues, such as the voice lines in Minnesota Fats - Pool Legend (#363).

Many other small tweaks and fixes to CD Block functionality have also helped improve compatibility with many games, including Ultraman Zukan (#329), Digital Dance Mix Vol. 1 - Namie Amuro, Sega Rally Championship Plus, Astal, Mizuki Shigeru no Youkai Zukan Soushuuhen (#391), and WipEout 2097/XL (#202).

The SCU has also received attention in this version. This time the focus was on various nuances of DMA transfers and timers, which led to stability improvements in Fighting Vipers, Sonic Jam, Tennis Arena, and probably many others.

As usual, there have been numerous graphics fixes to count here, most of them focused on small accuracy errors reported by testers. One fix that deserves to be highlighted is delaying the handling of VDP1 framebuffer swaps to slightly later in the same scanline which was meant to fix Marvel Super Heroes sprite glitches but has also fixed dozens of issues along with it:

• Flickering graphics in DragonHeart - Fire & Steel (#334), King of Fighters '96 / '97 (#272), Jantei Battle Cos-Player (#368), PhantasM (#336), Soviet Strike (#303), Virtua Cop 2, and Yellow Brick Road (#335)
• Corrupted sprites in Center Ring Boxing (#377), and Marvel Super Heroes (Shuma Gorath's Chaos Dimension move) (#72)
• Partially missing sprites in Fuusui Sensei - Feng-Shui Master (#405)
• Freezes/crashes in Mahou no Janshi - Poe Poe Poemy (#378), and Shockwave Assault (#406)

Another fix to highlight which wasn't as impactful, but is something that no other software-based Saturn emulator does right, is the VDP2 VRAM access cycle handling fix done to improve Doukyuusei - if's title screen while maintaining proper behavior for Capcom Generation - Dai-5-shuu Kakutouka-tachi's art gallery. The new behavior has been documented here to the best of my knowledge.

Finally, the last component to receive some fixes was the SMPC. Specifically, a couple of fixes to the way inputs are reported in SH-2 direct mode have fixed lack of input response in World Heroes Perfect (#297), Touge King the Spirits (#322), Chaos Control Remix (#348), and Father Christmas (#374). This leads us nicely into the next section.

Input system enhancements

Ymir now supports the Arcade Racer and Mission Stick peripherals in addition to the Control Pad and 3D Control Pad. The steering wheel sensitivity curve can be adjusted in the peripheral configuration window. The Mission Stick can be switched between three-axis and six-axis modes, the latter of which works great in Panzer Dragoon II Zwei as long as you have an extra pair of hands.

Almost the entire alphabet is mapped to this controller. Good luck using it with only two hands.

At a lower level, the input system is now capable of distinguishing various characteristics of input axes:

• Monopolar/bipolar: whether the axis value ranges from 0 to 1 or -1 to +1 respectively
• Absolute/relative: whether the axis reads a fixed value when held at a particular position or responds to continuous movement
• 1D/2D: the number of components of the axis

Here are some examples of each combination of characteristics:

1D	Monopolar	Bipolar
Absolute	Gamepad trigger	Steering wheel
Relative	-	Mouse wheel

2D	Monopolar	Bipolar
Absolute	Drawing pen, touchscreen	Gamepad stick
Relative	-	Mouse movement

With this, the emulator will now stop you from binding mismatching axes to input binds, such as trying to map a gamepad trigger to the Arcade Racer's steering wheel.

UI features

Several new options...

v0.1.6

Ymir v0.1.6

Discord | Patreon

This update, just like previous 0.1.x releases, brings a ton of compatibility fixes, more performance improvements, and a handful of new features to play with, including vertical display (TATE) mode, a basic notification/messages system, improved frame pacing stability in full screen mode, and emulation speed control. This is the biggest release yet, with over 80 changelog entries and the most bug fixes of every release so far.

Before we get to the meat of the release notes, I'd like to announce that Ymir now has an official compatibility list which still needs some love. Help fill it out by testing games and filling out reports in the Requests sheets. As of this writing, over 60% of reported titles are fully playable and another 20% at least goes in-game. Not bad for an emulator that's less than a year old! But this is only a small picture of the overall compatibility, as only 6% of the entire library has been tested so far.

Compatibility improvements

Here's a small showcase of games that now work on 0.1.6 or had major bugs fixed:

(click any image to zoom)

As usual, @celeriyacon has provided me with an ever-growing set of test ROMs to help improve emulation accuracy, while @Zet-sensei has pointed me in the right direction with various tricky games to test and fix, and the folks in the Discord community have been diligently testing dev builds and reporting issues left and right. This time, the SCU and the VDP2 have received special attention -- tons of fixes eliminated various bugs in previously working games and made a few more games boot past the SEGA logo or the typical black screens. WipEout is now playable and Rayman's graphics glitches have been eradicated for the most part. Even the famed Rayman final boss glitch is no match for Ymir.

ymir-wipeout.mp4

ymir.-.rayman.mp4

The SCU DSP in particular now has an even nastier set of tests, some of which Ymir is deliberately failing in order to maintain compatibility with some games. The SCU DMA has received an overhaul and is much more accurate, matching Mednafen's behavior 1:1. There are a few cases where both Ymir and Mednafen don't match the real hardware, although these are probably never seen on commercial titles. SCU interrupts have been revised along with master/slave SH-2 external interrupt handling behavior and should be much less problematic. The synchronization between SCU and the two SH-2 CPUs has been tightened, which helped fix WipEout's black screen on boot.

SH-2 cache emulation had a small bug in the LRU lookup table that caused weird glitches in many FMVs; this is now fixed and SH-2 cache emulation is now enabled by default for the added compatibility it provides for some games (e.g. Dark Savior).

There are too many VDP1 and VDP2 fixes to discuss here -- see the Changes section below for details. In short, many graphics glitches reported by users have been fixed, including some that no other emulator (except the MiSTer Saturn core, to my knowledge) has accurately emulated so far. A notable example is an issue with Capcom Generation - Dai-5-shuu Kakutouka-tachi (#254) in which the bottom portion of the pictures in the art gallery were sliced and shifted to the right, a behavior seen on Ymir 0.1.5, Mednafen 1.32.1, Yaba Sanshiro 1.16.6 and Nova 0.7.0:

This was caused by lack of emulation of an improper VRAM access cycles configuration made by the game for the bitmap graphics displayed on these screens. With recent improvements to VRAM access cycles handling, Ymir 0.1.6 is now capable of displaying the images correctly:

The newly improved VDP2 VRAM access delay debug window can display information on delayed background data accesses and has been upgraded to display information on bitmap backgrounds too:

If you're technically-minded and interested in how this works, check out my brief writeup on games that use illegal VRAM access cycles.

To conclude this round-up, there have been a few fixes to the CUE parser that should fix some CD audio track misalignments and allow Ymir to load games dumped with ImgBurn or other non-Redump-approved tools, as long as the audio tracks are still in raw/binary format. The CD Block, SCSP and SMPC received one small bugfix each:

• CD audio tracks in X-Men: Children of the Atom will now resume properly after pausing in-game.
• A SCSP bug that caused sound effects in many games to be truncated has been squashed. Enjoy Sonic R's pause jingle in its entirety, Alucard's hoohs and haahs while speedrunning Akumajou Dracula X, and Daytona USA CCE's over-the-top announcer lines uninterrupted!
• SMPC command processing was slowed down ever so slightly to allow finicky games such as F1 Challenge and the European release of Quake to boot.

TATE mode and new view options

A number of games (especially shoot-em-ups) support TATE mode, which requires the screen to be rotated 90°. Ymir now supports rotating the display in any direction to support those games, or just for added challenge. You can even rotate the display 180°, because why not?

Along with this, new aspect ratio options have been added along with options to quickly resize the window to specific scales. Note that the scales are relative to high resolution modes, so the 2x option will result in 4x4 pixels in low resolution modes and 2x2 pixels in high resolution modes, both of which fit nicely on a 1080p display. Also, there's a new option to remember window geometry (position and size) so you don't have to adjust the window every time the emulator is relaunched.

Smoother frame pacing

This version significantly improves frame pacing stability in full screen modes. The algorithm will now smooth out frame rate adjustments based on audio buffer state over the course of multiple frames and will spin-wait for up to 1 ms to ensure the frame is presented as close to the target time as possible. See the graphs below for a comparison.

Before:

After:

0.1.5 had slight fluctuations on every frame. 0.1.6 is far more consistent, as depicted by the nearly straight line and the more accurate 16.6ms frame time.

Performance improvements

Some components went through a round of performance optimizations:

• SH-2 cache emulation now avoids byte-swapping, making it slightly less impactful when enabled.
• SH-2 interrupt checks have been optimized down to a single flag check, noticeably improving performance as this is done millions of times per second.
• SCSP went through various micro optimization rounds that also contributed to a small overall performance gain.
• The memory bus can now map simple arrays directly, greatly speeding up accesses to ROM and RAM which comprises the majority of memory accesses.

Combined, these optimizations contributed to an overall emulation performance improvement of 5% to 10% on average and in some cases as high as 25%.

The biggest performance boost of this version comes from a new option in Settings > Video that introduces a separate thread for deinterlacing which significantly lessens the performance impact of that enhancement. In some games, the deinterlace option used to cut performance almost in half, but with the new thread the impact is usually less than 10%. This option requires a quad-core CPU or better for best results.

See the pictures below for a performance comparison in Virtua Fighter 2:

In this example, the performance cost of the deinterlace option was about 37%. With the dedicated thread, it drops to less than 8%. Some games benefit much more from this option than others. In Fighters Megamix, performance is lowered by 43% with the deinterlace enhancement, but when adding the dedicated thread, it reduces performance by less than 8% again.

Speed control

Before 0.1.6, the only speed options you had were 100% or uncapped (and pau...