Redump Forum

The PSX is using a small 8bit Motorola CPU with onchip BIOS ROM to control the CDROM drive.
The first BIOS dump was done some months ago via decapping: http://wiki.psxdev.ru/index.php/SUB-CPU
And that dump revealed that Motorola has included a nice test mode that allows to dump its BIOS via a few wires.
More on that here: http://www.psxdev.net/forum/viewtopic.p … &t=557 (for the wiring diagram skip ahead to this post: http://www.psxdev.net/forum/viewtopic.p … =557#p4174 )
For the whole PSX series, there should be around 25 different CDROM BIOS versions (for different regions and different revisions). Currently only 4 versions are dumped.
If you get some wires together, then there's still a good chance that you can be the first person viewing the binary for one of the missing versions.

Nice job!

So is it possible to identify undumped ones by just looking at the mobo?
I don't have soldering equipment, but I might be able to send you some mobo's if I get them back in 1 piece (live near the German border).. Anyway, I guess you already dumped most PAL models that I have here.

Also, can you tell us what use these dumps will be? Can they help improve emulation?

Finally, are you planning to release the files? I see that MESS already added the decapped one: http://www.psxdev.net/forum/viewtopic.p … &t=431

Jackal wrote:So is it possible to identify undumped ones by just looking at the mobo?

Yes, the "SC4309xx" names on the 52pin chips seem to be unique for each version/region. The older 80pin chips do probably also have some unique names (current rule-of-thumb is that 80pin chips aren't dumped, not matter of their name). The dev-board EPROM version http://upload.wikimedia.org/wikipedia/c … PU1_01.jpg has some sticker saying '94 11/28, that's also undumped, despite of the EPROM socket).

NB. when looking at the mainboards: It would be very nice to take photos/scans of their front & back sides. Such pictures are still quite hard to find in the internet.

Jackal wrote:Also, can you tell us what use these dumps will be? Can they help improve emulation?

The long answer is that the cdrom bios (or "drive firmware") controls this stuff: http://nocash.emubase.de/psx-spx.htm#cd … controller
PSX games are sending commands like ReadN, SetLoc, GetStat to the cdrom sub-cpu: http://nocash.emubase.de/psx-spx.htm#cd … andsummary Currently, PSX emulators are using high-level emulation to reproduce that commands, although nobody really knew what those commands were doing internally. Using low-level emulation for the 8bit CPU and the attached cdrom chipset should make emulators much more accurate...
But, in practice, most PSX games seem to be happy with high-level emulation either (I've emulated the whole stuff in no$psx last week (99% finished, but not yet released), and the overall effect was that it did make the the emulation slower, especially due to longer spin-up & sled-move times, but it didn't fix problems with game that did hang during cdrom loading - at least I do now know that those problems seem to be related to something else than cdrom emulation).

Jackal wrote:are you planning to release the files?

Rather not. The built-in dumping function is spitting out the whole binary in form of a "hexdump.txt" file, but I guess there's some copyright envolved nonetheless. Anyways, it's a pretty simple DIY project to dump it.

If somebody wants to send PSX mainboards to hamburg/germany, I could dump them for you (and return the boards... as long as I don't have to bother about the postage).