Does anyone know how to make a multi game ps1 disc?

[vstar950]

Back in the ps1 days there were people that made multigame discs. One of my favorites was doom,final doom, duke 3d, duke manhattan project, duke land of the babes, and tenka. How did they do this? Is there a more modern simplified way nowadays? Is it possible to do this with multidisk games like re2, but use only one disk? I would like to make my own collection like this from my own game collection. In these ges, there was a menu to choose which title you wanted to play. Then you would select it and play. They also did this for a 31 in 1 cheat device disc with codebreakers and different gamesharks, and caetla.

This is what that cheat disc is. They made a better one. Look for a 2018 or 2021 link

Ps1 Cheat Engine Compilation

 

[FAST6191]

Missed that being a thing back in the PS1 era, though most games I cared about pushed the sizes a bit anyway.

Looking at a still active site from that time (don't think I can link it as its sister site has current PC game cracks) the tool of choice was probably PSX MultiGamesCompiler, seek a tutorial for that. Looking at said tutorial it mentions only exe launched games (PS1 also uses the extension exe, nothing to do with the Windows format) as being viable. Will have to look and see what the underlying tech is for all this, that said for the exe stuff (which is a lot of games) then it looks basic enough to pull off.

Merging discs has two main problems.
1) Potential sizes issues generally* or within the formats themselves. Granted CD is probably below this limit in most regards (16 bit addresses would not work, 32 bit is around 4 gigabytes) so maybe if those optical drive emulators get it going on then something interesting could happen.
2) Games doing things differently -- one of the more famous things related to all this is Final Fantasy 7, the same whole game is on each disc but with different videos for the cutscenes such that you can do a disc swap (the same spring trick you use for your cheat cartridge being in play) and play the game but with different cut scenes playing at the "appropriate" point. Trying to make that work in the several gigs disc scenario would see you have to make the game load different files and at that point we are into big boy ROM hacking (only just but still there) and far from the simpler scenario you asked for.

*the only reason to press multiple discs back in the PS1 era was because you can't fit all the data on one CD (I doubt they would have been nice enough to give you multiple discs for network play or multi screen). Despite however many years it has been I doubt you will be able to usefully compress things down and still have it run on a PS1 (emulators might be a different thing -- plenty will play MP3s instead of audio tracks, and I imagine you could do similar for video and blank out videos but have your PC or something play a nice AVI file with a Lua script from the emulator itself). At the same time the guide I was seeing was referencing ripping (in the classical removing things to make games smaller sense of the term rather than grabbing data that most assume today) so there is that option in this.

I could do the general case for multi disc as it is much the same regardless of system, though file based affairs have an easier time than some older ROM based things.

1) Drive level fun.
If you can force the drive to read a different track/session/partition/whatever delineation makes sense for your system then that is the easy way. Not all systems will have provisions for this, and while it is within the purview of PS1 mod chips as I understand them then most won't have anything like this built in. If and when optical drive emulators/ODEs/ODDEs finally come on the market for the PS1 (I believe the variety of drives makes such things a bit harder than some other systems that keep with a simple enough drive style to make a general case).
For older systems based on cartridges then games get made to work on certain addresses and read from certain locations (though it can happen for the PS1 as well -- Square (Enix) having some notable things for this with audio being outside the file system, though it was more prevalent on the PS2). Trying to make things read from different addresses, especially for the PS1 where code could and would do all sorts of fun maths and jump around (your average NES game is less this and more likely to be levels 1 through 8 in a line with no annoying extras/minigames), is a nightmare hack that might take years to complete. There is a fun challenge/speedrun thing some do with older systems that share a cartridge type as they substitute things such that you variously play different rooms on different games and with fairly minimal hassle but we of topic somewhat now so I will leave that.

2) Jump loader.
Loads a piece of software ahead of time and then jumps to the one the user selects. Hopefully no files are named the same but are different if you don't allow subdirectories. In the case of the one I saw above it is limited to exe stuff (very popular format but not all of them as devs were still inclined to push limits and colour outside the lines somewhat back on the PS1)

 

[KleinesSinchen]

1) Potential sizes issues generally* or within the formats themselves. Granted CD is probably below this limit in most regards (16 bit addresses would not work, 32 bit is around 4 gigabytes) so maybe if those optical drive emulators get it going on then something interesting could happen.

Sadly the internal addressing system on CDs is not a 32-bit integer (which would allow enormously many sectors), but weird BCD stuff, ranging in the best case from 00:00.00 to 99:59.74. The CD can't deny the origin as pure audio storage. Each second has 75 sectors (2352 bytes total, 2048 bytes when used for data after subtracting parity bits/error detection/error correction)

Some CD-players (and DVD-players in CD mode) fail going beyond 90 minutes, many fail at 99:59.74

Despite the addressing system depending on decimal numbers, I got the hexadecimal 0A:00.00 as sector number when going beyond the 100 minute mark (1100MB SVCD). I guess it is no coincidence that high-capacity, narrow track CD-R maxed out at 100 minutes (many 90min/800MB CD-R actually go to about 93:30min, while 100min/870MB CD-R don't go much further). My DVD players crashed at the magic position, while the PC drive can read the full thing in RAW mode.

I've no idea how an optical drive emulator -- or the PlayStation itself -- would react when trying to address too high sector numbers. Physical PS1 CDs are -- as far as I know -- limited to the older 74min/650MB. I wouldn't want to torture the aging drives with narrow track, out of specification, CD-R just to gain a bit more storage (878MB at best). I was surprised to hear the drive running much smoother and more silent when using old 74min rather than current, normal 80min CD-R.
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I can't answer the initial question "How to make multi-game PS1 discs?", but I fail to see much use in it anyway: Since many games contained CDDA tracks and/or "full motion video" (wasn't that some marketing phrase at the time?) to show off what CD based consoles could do over cartridge based systems of the time, we could hardly fit multiple full games unmodified and lossless on one CD.
For some smaller games it would be a nice thing to have (and I would be interested in doing it myself).