No$psx Emulation Files Contents

CDROM Images
CDROMs are supported via complete disk images (in .CCD+IMG, .CDI, .CUE+BIN, .MDS+MDF, or .NRG format), via single-track images (.ISO files), or as raw executables (.EXE files).
Decompressing .ECM and .CDZ files is supported. Subchannel data (for libcrypt'ed games) can be read from .SBI, .M3S, .SUB, .MDF files. Reading from real CDROM drives is also supported, but does require wnaspi32.dll (which appears to be a problem on WinNT/Win2K and higher).

Memory Card Images
Memory Cards are stored as 128Kbyte .MCD files in MEMCARD directory. If a CDROM image is loaded, then the first memory card (for machine 1, slot 1A) will be assigned to "<cdrom_filename>.mcd". The other memory cards (for other slots or other machines) are just using general filenames: ""; with MM=Machine (01 and up), N=Slot (1 or 2), X=Multitap Sub-Slot (A..D).
To manage files in memory cards via BIOS boot menu: Eject CDROM and reset emulation (to get to the boot menu), then load a CDROM image with the Autostart checkbox disabled in lower-left (this will load the corresponding memory card alongsides with the CDROM, and stays in boot menu as autostart is off).

No$psx contains its own PSX BIOS clone. Optionally, a copy of the original PSX BIOS can be stored as file PSX-BIOS.ROM in no$psx folder. Doing that may be useful for two purposes:
Compatibility Issues: There are no known problems, but please let me know if you discover a game that works only with the original BIOS, but not with the nocash BIOS.
Font Issues: The nocash BIOS doesn't contain its own SHIFT-JIS font (this font is used by a few games; mainly in memory card screens). By default, the nocash BIOS copies the font from PSX-BIOS.ROM (if it is present), otherwise it uses fonts from the operating system: The so-called "MS Gothic" font (if you have japanese fonts installed on your computer), or otherwise "Courier New" (which covers only latin letters of course).
Notes: There's is also a setup option to select between nocash BIOS and original BIOS (the default is to use original BIOS, if present). Aside from using the fixed PSX-BIOS.ROM filename, you can also select .ROM files in the CDROM loading screen (useful if you want to test different BIOS versions).

Expansion ROM Image
Expansion ROMs can be loaded via CDROM loading screen. Supported file extensions are .ROM (raw rom-image) and .FCD (encrypted Xplorer rom-image). The files must contain valid Expansion ROM IDs at offset 004h and/or 084h, otherwise they are treated as normal BIOS ROMs. Typical expansion ROMs are Cheat Device firmwares; there is no real use loading these into no$psx, except for viewing them in the debugger.
Note: Some expansions do work only with original Sony BIOS (for example, Caetla is using various hardcoded BIOS addresses which are incompatible with no$psx BIOS clone). On the contrary, Xplorer is working only with no$psx BIOS clone (with Sony BIOS it would place a COP0 break inside of a branch delay, which isn't supported by no$psx). Action Replay may refuse to start GPU transfers unless the GPU is NOT ready for transfer (due to misunderstanding GPU status bits) (this does actually 'work' on real hardware because the GPU isn't <instantly> ready, but that effect isn't yet emulated in no$psx, so it works only when manually skipping the faulty waitloop in the debugger).

If present, file MC68HC05.ROM (16.5kbytes) is loaded automatically as CDROM BIOS image (alternately it can be loaded manually via file menu, which treats any 16.5Kbyte .ROM file as CDROM BIOS image). The file used ONLY if low level CDROM BIOS emulation is enabled in setup.
In low level mode, timings and responses to cdrom commands are closer to real hardware, which might be useful for bug testing, but otherwise it isn't too useful or recommended (the more accurate seek times are making the cdrom emulation much slower; the SCEx protection is also emulated, meaning that region problems may occur when using a CDROM BIOS version that doesn't match the CDROM DISC region).
In the debugger, use Ctrl+T toggle between MIPS and HC05 disassembler view. The TTY window can log various HC05 I/O events (eg. Spindle and Sled control).

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extracted from no$psx v2.2 - homepage - patreon - whole doc htm/txt - copyright 2022 martin korth (nocash)