Weird PS1 Issue / Might Need Repair Hey guys, Recently on my blue debug PS1 I've been getting some errors which I think is either a hardware failure or something is up with the BIOS. The issue is that the PS1 will not boot games anymore. It see's there's a game there, attempts to boot it, and crashes at the PS logo. It'll boot all the way to the PS logo, but the 'Produced by Sony Computer Entertainment' text is kinda garbled (the word 'Produced' is garbled to 'by by'). The lens is not the issue at all though. It was a new lens I had only just installed and I've since pulled it and tested it on two other units, and it works perfectly fine. After it attempts to boot the game, it crashes to a distorted black and white PS logo. Sometimes this doesn't happen and it actually boots further but never boots the game. Somehow it's failing to get past the initial boot sequence on any game. I've tried Gameshark (that plug into the back of the unit) and they bypass all of that but fail to boot a game. The only thing I can think of is that the BIOS has become corrupted. The system boots audio CD's fine, reads discs in Gamesharks built in CD Explorer... but won't boot a damn game! I've already opened and inspected the board and have found no signs of burnt out components, blown capacitors, or any sort of flashing. I feel like it maybe something small like a diode or other small component. I've tried swapping PSU's, power cords, data cables, and nothing has worked. Can you guys advise me further on this matter. Maybe there's someone here who can look at my PS1, perhaps even repair it?
I've seen scrambled boot screens on machines with bad RAM - I don't think it's the boot ROM, because that black screen with the PS logo that's getting corrupted isn't in the ROM, it's read from the CD.
In this case, I doubt it - in order to play CDs, pretty much all of the CD control subsystem has to be operating correctly, and I can't see that happening with a busted mechacon. On top of this, the console clearly has to be able to read data from the CD, because otherwise it wouldn't even get to that black boot screen. This is why I suspect it's loading the license screen data into bad RAM (hence the corruption) and then loading the boot file into bad RAM (hence the crash).
If it's the RAM then nothing too hard to replace but depends on what version he has - 100x - 55xx have 4 small RAM chips while 700x and up have just a single chip for the RAM and if I'm not mistaken it's usually the TOSHIBA C20518 chip under the CXD8606BQ. I used to take that chip off dead boards and use it on a S3 Trio PCI video card and it fit in the empty RAM slot on the PCI card.
Since it's a blue debug, it's presumably got either a PU-7 or an early PU-8 in it, and they both had the 4 chip RAM layout. The biggest problem would be getting replacement RAM chips, since they are old EDO memory, and haven't been in production for about 15 years. Probably the easiest source would be a retail board.
Easiest source = dead PU-18 board,since they didn't change the RAM chips until 700x. BTW,I've seen somebody on PSXDEV who upgraded a PU-18 board to 4 or 8MB RAM. No jokes.
It's 8MB - using 4 x KM48V2106AJ-6 - basically the same arrangement as the DTL-H2000 devboard. I was the person that originally did it. Incidentally, there are PU-8s that only have a single RAM chip on them.
This one seems to have been made early 1998 - and it has Toshiba RAM on it. http://wiki.assemblergames.com/lib/exe/fetch.php?media=wiki:sony:pcbphotos:pu-8_v2.jpg
So the RAM took a crap on me. It's odd how everything else loads find though. Do you guys know anyone who could repair it for me? I'm not so good with soldering small parts like that.
It's a educated guess, but I have seen RAM failures causing exactly the sort of problem you have. I'm sure there is someone on the forum that could swap the RAM over (I would offer to do it, but I'm in HK and shipping would be slow and expensive).
I had a similar problem with a SCPH-1002 Wouldn't boot games and instead of saying "licensed by" There would be a gap and it would say "ed by ed by" or something along those lines. I would do a close inspection of the motherboard using a strong magnifying glass to see if any contacts are damaged or loose. Sounds like a BIOS error though. Not sure if you can flash the PS1 bios.
He could take another PS1 BIOS chip from another board and solder it to the system using a soldering station. I've seen somebody do that with success.
I heard of 4mb being done back in the 90's, I don't know why they couldn't get 8mb to work (it might be a CPU revision problem but I always suspected that they just did it wrong). In the arcade there are CPUs with 16mb, GPUs with 2mb and a mythical SPU with 2mb. Whether it's possible to hook that up in a console is another matter, they can also be clocked at 50mhz instead of 33mhz but that might cause timing issues if the games don't expect it.
Seems unlikely - the contents of that black "licensed by" screen are read from the CD, they aren't in the boot ROM. And, for reference, you can't reflash it - it's a mask programmed device that was built that that specific code in it. I think they probably just did it wrong - getting the 8MB to work was easy once I realized that the memory controller was basically designed to work with 8MB of RAM and the 2MB configuration in the retail console was being handled as a special case. The first hint was that even on a retail the A0 line on the DRAM was getting A2 during RAS and A13 during CAS - which would be correct for a device with a 2K page size, but not for the (1K page size) RAM that was actually fitted to a retail console. A bit more poking around with the logic analyzer revealed that DRAM A8 was being used to fill in the missing address bit caused by the page size mismatch (and A9, although it had the wrong data during CAS/ didn't matter because the device only had 512 column addresses) - and that it was connected to the CPU pin that you would expect to be DRAM A11 - the "real" DRAM A8 pin did exactly the right thing for a 2K page size chip. At that point, it just became a matter of swapping the RAM chips, connecting A8 to the right place and adjusting for the other pinout differences between the two devices - and it worked first time. It didn't even need a boot ROM patch because the default setting for the memory control register used by the retail boot ROM was already capable of supporting 8MB. As for getting 16MB to work, it might be interesting to see what the arcade boards set the memory control register to - using the default setting in the boot ROM, the CPU throws an exception if you try to access past 8MB, and I would have expected to see 0xffffffff if it was reading unimplemented memory. There is a second RAS/ line coming from the memory controller, and it is definately active in some modes (for example, if you write 110 to bits 9-11 of 0x1f801060 then the second RAS/ line is asserted on accesses to the 2MB above the standard 2MB memory). I have seen a PSone with a 2MB SGRAM chip on the GPU, but I couldn't get it to do anything interesting, despite the fact there are enough address lines to theoretically address 4MB. There is also an extra chip select line on the GPU, so it might be interesting to see if that can be got to do anything.
