20260813

This is the first release under the z486 name. The CPU and MiSTer core were
previously named z386x and z386_MiSTer; the new names better reflect the core's
pipelined design, hardwired instruction paths, integrated x87 coprocessor, and
486-class performance.

This release includes:

• Experimental x87 floating-point support. It is not yet complete, but is
  sufficient to run Quake.
• Faster common x87 arithmetic and memory operations. Quake 1.0.6 now reaches
  6.6 FPS, up from 2.7 FPS with the initial implementation.
• CPU speed adjustment for software that cannot tolerate the full CPU
  speed.
• Compatible with ao486's sysctl.exe for CPU speed selection. This allows the
  0MHz Lemmings 1 image to run correctly in high-performance mode at the 30 MHz
  setting.
• A reorganized CPU implementation with clearer functional-unit ownership and
  updated z486 architecture documentation.

Installation

This release requires the included updated MiSTer binary, because the core
identity changed from Z386 to Z486.

Put the files in these locations:

• MiSTer in /media/fat, after backing up the existing file.
• z486_20260813.rbf in /media/fat/_Computer.
• boot0.rom, boot1.rom, and disk images in /media/fat/games/Z486.

Disk images previously stored in /media/fat/games/Z386 must be moved or
copied to /media/fat/games/Z486 for this release.

20260806

This release focuses on compatibility and protected-mode correctness:

• Fixed 386 task switching used by Bubble Universe.
• Fixed the interrupt shadow after MOV SS and POP SS, preventing
  input-dependent crashes in Settlers II.
• Improved Windows 3.1 compatibility, including precise instruction-fetch page
  faults and the repeated right-edge strip in 1024x768 modes.
• Added BSWAP and corrected several CPU-identification behaviors used by
  HWiNFO's processor errata tests.
• Fixed Rusty's clipped intro framing by showing VGA overscan by default.

Put MiSTer in /media/fat, z386_20260806.rbf in
/media/fat/_Computer, and boot0.rom, boot1.rom, and disk images in
/media/fat/games/Z386.

20260728

This release focuses on VGA/SVGA compatibility.

• Fixed planar SVGA framebuffer reads and writes used by Windows 3.1, including VGA latch loading and map-mask behavior.
• Fixed stray pixels in Superfrog (#38) by preserving ordering for VGA aperture accesses. Verified on MiSTer hardware.
• Fixed adjacent bytes of wide I/O writes so edge-sensitive peripheral ports receive separate strobes.
• Fixed coherent PIT counter reads.
• Enforced the selected 16, 32, 64, or 128 MB physical memory boundary.
• Added a persistent simulator control interface for remote keyboard/mouse input, screenshots, checkpoints, and clean shutdown.
• Improved simulator video rendering, performance, tracing, and checkpoint support.
• Added platform regressions for SVGA memory behavior, PIT I/O, memory sizing, and wide I/O writes.

Put MiSTer in /media/fat, z386_20260728.rbf in /media/fat/_Computer, and boot0.rom, boot1.rom, and disk images in /media/fat/games/Z386.

20260725

This release improves both performance and compatibility:

• Doom timedemo performance improves to 29.7 FPS at maximum detail, up from
  27.3 FPS in the previous release and 21.0 FPS on ao486 using the same MiSTer
  system.
• Added more CPU pipeline and instruction fast-path optimizations, including
  faster SHLD/SHRD and more effective branch-target prefetching.
• Fixed Windows for Workgroups 3.11 enhanced-mode startup, display colors,
  unexpected exits from Program Manager, and software mouse-cursor trails.
• Fixed HWiNFO Mainboard info, warm reset, and several cache-coherency and
  protected-mode I/O problems.
• Fixed VGA read/write ordering artifacts seen in Lemmings and other software.
• Added support for 64MB and 128MB MiSTer SDRAM modules, including correct
  guest memory-size and CMOS reporting.

Update: Added z386_20260726.rbf, which fixes unstable Landmark benchmark
results and should also improve other timer-based CPU speed tests.

Put MiSTer in /media/fat, z386_*.rbf in /media/fat/_Computer, and
boot0.rom, boot1.rom, and disk images in /media/fat/games/Z386.

20260711

• More performance work - frontend improvements and hardwired fast paths for common instructions.
• Doom timedemo performance improves to 27.3 FPS, +30% compared with 21.0 FPS on ao486.

Known issues: intro artifacts in King's Quest IV and hang in Tyrian.

Put MiSTer in /media/fat, z386_*.rbf in /media/fat/_Computer, and boot0.rom, boot1.rom and disk images in /media/fat/games/Z386.

20260629

• @odiaboeeu: MPU-401 UART MIDI output (ports 330h/331h).
• @odiaboeeu: PC gameport joystick (port 201h).
• DDR VGA framebuffer - SVGA should work now (SimCity 2000 and others).
• CDROM and CD-DA support.
• Selectable RAM size (16/32/64/128 MB).
• Fix hangs: Lemmings 1 & 2.
• Use 8KB cache sizes.

Put MiSTer in /media/fat, z386_*.rbf in /media/fat/_Computer, and boot0.rom, boot1.rom and .vhd files in /media/fat/games/Z386.

20260623

• Implements 80386 early-start for faster memory accesses.
• Vairous other performance optimizations.
• Doom max details fps 23.0, faster than ao486's 21.0.

Put MiSTer in /media/fat, z386_*.rbf in /media/fat/_Computer, and boot0.rom, boot1.rom and .vhd files in /media/fat/games/Z386.

20260613

• Improve performance (Doom max details fps 19.2 vs 17.8). Better CPI through TLB fixes, lower latency for memory accesses, and dcache improvements.

Put MiSTer in /media/fat, z386_*.rbf in /media/fat/_Computer, and boot0.rom, boot1.rom and .vhd files in /media/fat/games/Z386.

20260610

• Floppy works now (#2)
• Improve performance (Doom max details fps 17.8 vs 16.6)

Put MiSTer in /media/fat, z386_*.rbf in /media/fat/_Computer, and boot0.rom, boot1.rom and .vhd files in /media/fat/games/Z386.

20260503

• Added audio/video and hardware menu options
• Improved keyboard compatibility: Prince of Persia 2
• Improved mouse compatibility: King's Quest VI
• Fixed sound quality issues
• "Reset and apply HDD" now works

Put MiSTer in /media/fat, z386_*.rbf in /media/fat/_Computer and .vhd files in /media/fat/games/Z386.