NeoCD-Libretro

Introduction

NeoCD-Libretro is a complete rewrite of NeoCD from scratch in modern C++11. It is designed with accuracy and portability in mind rather than being all about speed like the the older versions. The goal is also to document all I know about the platform in the source code so other emulator authors can make their own implementations.

What is different?

• It's accurate. A lot more. As a result it uses more CPU power than older versions but requirements are still modest: NeoCD runs perfect on Raspberry Pi 3 for example.
• It's implemented as a libretro core which allows it to be used everywhere, at home or on the go :)
• The CD-ROM drive is now emulated at hardware level.
• Supports savestates
• Supports rewind

Credits

NeoCD would not have been possible without the following people generously sharing their code:

• Karl Stenerud - Musashi 68000 Emulation Core
• Juergen Buchmueller - Z80 Emulation Core
• Jarek Burczynski & Tatsuyuki Satoh - YM2610 Emulation Core
• The MAME Development Team - MAME, an invaluable source of knowledge about arcade machines.
• Romain Tisserand - libchdr (https://github.com/rtissera/libchdr)

Installation

Core files

Copy the libneocd_libretro library to RetroArch/cores.

The INFO file (cosmetic)

Copy neocd_libretro.info to folder RetroArch/info

Required BIOS Files

To function NeoCD need a BIOS from a Front Loading, Top Loading or CDZ machine. The BIOS files should be installed in a neocd folder under RetroArch's system folder. NeoCD will look for any .bin or .rom file in the neocd folder and any folder under it. It will also look into .zip archives. BIOS files are identified by contents so the name of the files don't matter. File hashes do not matter either.

BIOS

📓 Note: You need at least one in the following table. If several BIOSes are available, it will be possible to choose which to run in the Core Options Menu. The files will be automatically byte swapped if needed.

📓 Note: The hashes are given to help you verify the files have not been tampered with, the emulator doesn't verify them.

Description	Filename	SHA1
Front Loader BIOS	neocd_f.rom	a5f4a7a627b3083c979f6ebe1fabc5d2df6d083b
Front Loader BIOS (SMKDAN 0.7b DEC 2010)	neocd_sf.rom	4a94719ee5d0e3f2b981498f70efc1b8f1cef325
Top Loader BIOS	neocd_t.rom	cc92b54a18a8bff6e595aabe8e5c360ba9e62eb5
Top Loader BIOS (SMKDAN 0.7b DEC 2010)	neocd_st.rom	19729b51bdab60c42aafef6e20ea9234c7eb8410
CDZ BIOS	neocd_z.rom	b0f1c4fa8d4492a04431805f6537138b842b549f
CDZ BIOS (SMKDAN 0.7b DEC 2010)	neocd_sz.rom	6a947457031dd3a702a296862446d7485aa89dbb
Front Loader BIOS (MAME)	front-sp1.bin	53bc1f283cdf00fa2efbb79f2e36d4c8038d743a
Top Loader BIOS (MAME)	top-sp1.bin	235f4d1d74364415910f73c10ae5482d90b4274f
CDZ BIOS (MAME)	neocd.bin	7bb26d1e5d1e930515219cb18bcde5b7b23e2eda
Universe BIOS CD 3.3	uni-bioscd.rom	5142f205912869b673a71480c5828b1eaed782a8

CD Images

In the era of modern computers and portable devices, CD-ROMs are no longer convenient. Additionally I believe it is not possible to read the TOC of protected games without special drivers. As a result, NeoCD now exclusively run using CD-ROM images.

NeoCD accepts as input a cue sheet file (CUE) or a MAME CHD file. CUE images can be either of "single file" type (CUE, BIN) or "multiple files" type (CUE,ISO,[WAV/FLAC/OGG]).

🎶 Supported audio formats are: Wave (.wav), FLAC (.flac) or Ogg Vorbis (.ogg)

The Core Options Menu

• Region: Change your Neo Geo CD's region. (changing this will reset the machine)
• BIOS Select: Select the BIOS to use here if you have several (changing this will reset the machine)
• CD Speed Hack: This will replace the BIOS CD-ROM busy loop with a STOP instruction, to help low powered platforms (like Raspberry Pi) load faster (optional, changing this setting will reset the machine)
• Skip CD Loading: Settings this to ON makes the emulator auto fast forward CD loading sequences.

For Developers

Project Dependencies

• A C++11 compiler
• libFLAC
• libogg
• libvorbis
• zlib
• MSYS2 (Windows)

Compiling

• Make sure the development packages for libFLAC, libogg and libvorbis are installed.
• Eventually, edit the CFLAGS in Makefile to suit your platform (Raspberry Pi...)
• Build: make -j 4
• Copy the resulting library in RetroArch/cores
• Done! (see the user section for the rest)

Tested platforms

• x64 / Windows / GCC 10.2
• x64 / Arch Linux / GCC 11.1
• Raspberry Pi 3 / Arch Linux / GCC 8.2

Known problems

• On Raspberry Pi set the CPU governor to "performance" to avoid possible micro stutter.
• In Metal Slug 2 sound glitches occasionally on Front or Top loader BIOSes, use the CDZ bios.
• In Galaxy Fight the raster effects glitch in demo mode but strangely work fine when playing.