PSX CD Boot Layout

No. You can use any name as long as it is referenced in the file SYSTEM.CNF.

 

I know you can use any name for the PSX.EXE what i'm saying is when it's named as SLUS, SCES, SLPS it takes into account the 3rd letter P=SCEI, E=SCEE, U=SCEA, .=same as console region, when it's named as PSX.EXE or something different it defaults to the same region as the console.

SCES Sony ComputerEurope Software (Sony Published Games)
SCED Sony ComputerEurope Demo (Sony Published Demo Disc)
SCPS Sony Computer Published Software (Sony Published)
SLED Sony LicensedEurope Demo (2nd/3rd Party Published)
SLES Sony LicensedEurope Software (2nd/3rd Party Published)
SLPS Sony Licensed Published Software (2nd/3rd Developed Games, Published By Sony)
SLUS Sony Licensed United States Software (2nd/3rd Party Published)

Some unknown at present:

PSX: Playstation Executable?
Demo Disc:
PBPX (Found on some Demo discs)
SLPM
LSP-

 

The "SCEA tm" text comes from the CD controller. The BIOS sends CD controller command 0x1A, and the drive will respond with 8 bytes. The 5th through 8th byte will be the ASCII letters 'S', 'C', 'E', 'A'.

The CD controller's response to command 1A, if the disk has passed protection checking (which it has if you're on this black screen), contains the first copy of the "wobble groove" copy protection data that passed muster. For normal consumer retail models, that is only one string, so it will always match the region of the console, like SCEA for American consoles. Mod chips send "SCEISCEASCEE" continuously while active; the first one to match the region is accepted by the CD controller. This is why foreign games on a modded American system will show, for example, "Licensed by Sony Computer Entertainment Europe" "SCEA tm" when a PAL game is inserted.

On Debugging Stations and Yarozes, command 1A will return four ASCII spaces (0x20's) as this region code. This causes the bottom region code to not display at all. There appears to be something in the BIOS to suppress the "tm" when the protection string is four spaces so as to not look silly. Debugging Stations ignore the wobble groove data and always pass protection. Yarozes look for "SCE" and ignore the last letter, allowing all regions' disks.

Japanese Midnight Blue (10 million celebration) systems, a.k.a. SCPH-7000W, appear to act just like Yarozes. I suspect, in fact, that they can boot the Yaroze boot disk, but don't have a Yaroze boot disk to try using with my SCPH-7000W. The SCPH-7000W does not show SCEI tm. In fact, the SCPH-7000W has an American BIOS, and I suspect that it's to allow non-Japanese games. Unlike the Yaroze, whose BIOS is old enough not to care, the SCPH-7000 BIOS has the license area check that black screens or similar if the license area is not Japanese. Thus by using an American BIOS with a Yaroze CD controller, you can call it a Japanese system, so long as you don't care if the CD player and memory card screens are in English instead of Japanese. (All NTSC PS1 systems I've ever seen are tolerant of both 100V and 120V, and of both 50 Hz and 60 Hz.)

American and European PS1s don't check the license area for validity. There are, in fact, tools to use arbitrary flat-shaded simple 3D models instead of the default "PS" logo. PS2s care, because they use a slightly modified copy of the PS1 BIOS for compatibility booting. PS3s don't care: the PS1 emulator in a PS3 has an American PS2 BIOS image file from which it boots the emulated PS1. The BIOS file is American regardless of the PS3's region.

 

Nope. Executable name doesn't affect that string at all. You can name executable anything (8.3 limit) but you must specify that name in the SYSTEM.CNF.
The reason it matches is because Sony assigns unique product code to each game/software and that product code contains a region character (I, E or A) for the supported region.



1 - Displays string based on the license data found on the game CD.
2 - Displays string from the CD controller in the console.

1 can be changed by modifying the license data on the CD but 2 can't unless you swap a CD controller.

 

Japan BIOS block booting of discs with mismatched boot sector data only because it was the quickest solution they could come up with to stop people from using the spring thing on the CD lid for playing inports exploiting the CD player disc swap bug. After they solved the swap issue adding the second check at the SCEx PS1 logo screen they didn't remove the code which checked for the logo. So it sat there for years.

As Myria mentioned, original behavior of Japanese BIOS was just skip the logo altogether if the logo data was wrong.

 

True for the original PSX, but the European PSone has got a territory check in the BIOS and won't boot non PAL discs.

I suspect the reason that the US boot ROM doesn't have the check is that it's also used in the Asia region consoles, and they will only boot Japanese discs. I also suspect that the SCPH-7000W is based on the SCPH-7003, since it has the wide-range PSU and the US BIOS - in that case, all Sony would have needed to do was change the mechacon chip for a Yaroze one.

 

I wasn't aware of that, pretty amazingly the "onechip" manages to clobber the check in rom http://www.fatcat.co.nz/psx/install/102/pm41_26w.html

Overriding a bit in a rom isn't a new concept, but I haven't seen it down with so few wires before (some of the Dance Dance Revolution bootleg dongles used a similar method to stop you bootlegging the bootlegs).

 

It's actually amazingly simple - it just monitors a single address line and waits for it to go high a couple of times, then does a short delay using NOPS and drags down a single data bus bit. I bet it was fun to work out, though.

 

The figuring out is always the hard part. I wonder if it copes with the different rom revisions.

 

Not likely, but it probably doesn't need to. Getting it right on a slow chip like a 12C508, though, without it being connected to the system's clock... Also, the part of the ROM that needs to be patched is compressed. All in all, it's a real pain in the ass to do without corrupting a lot more than just your target instruction. I'm amazed that they got it working reliably.

I had no idea that Sony had bothered to put BIOS-based region checking into the very last European PS1 model like that. Not even the SCPH-9002 had it, as far as I know.

 

PSone's can come with BIOS 4.3, 4.4 or 4.5. I don't know what happened to 4.2 as that hasn't turned up on anything so far.