SNES CD/Nintendo PlayStation Works - Sort of?

http://kotaku.com/fabled-nintendo-playstation-console-only-cost-75-at-au-1741037676

I was skeptical at first when I read that they couldn't get the CD portion to do anything, but close to the end of the video when they boot it up, it shows some interesting stuff.

So, who wants to volunteer to get that pesky disc drive running?

 

The obvious place to start would be dumping the ROM in the cartridge and finding out what the CD ROM test does. My guess is that the basic electronic design is going to have a lot in common with the old proprietary interface Sony CD-ROM drives of the time (Like the CDU-31 and CDU-33). That CD DSP was also used in some Sony audio CD players, so the documentation on that should be fairly easy to obtain. The chips on the actual CD-ROM drive board look fairly normal - the QFP is going to be the RF amp chip (the number looks like it's CXA1272, which is plausible) and the Rohm chip with the BA prefix is a BTL driver to run the motors and actuators on the drive.

Most of the other parts on the board are standard SNES parts - the only oddities are that it has 2 stereo DACs (presumably one for the SNES side and the other for the CD-ROM) and a couple of other chips in the CD-ROM area (the SOP chip is probably just a bus buffer, the QFP could be anything, and doesn't appear to be marked). Those Sony chips were designed to be controlled by a MCU, and although the chip on the top board with the LCD is an MCU, it's a 4-bit part and would seem a strange choice for a CD mechacon - so it's possible that's just running the display and the load/eject side of things and the other QFP (with the patch wires) is the main mechacon.

This the datasheet for the MCU on the top board:

http://pdf1.alldatasheet.com/datasheet-pdf/view/7076/NEC/UPD75P308.html

It's hard to read the number, but it seems to be the GF plastic OTP variant, which would make sense - a quick look at the board suggests that the lines marked on the datasheet as being backplane and segment drives are running to the LCD, which also supports the idea that it's this chip.

 

I'm curious, why would you start a separate thread?

 

Because it's news, and people aren't exactly going to see it if I simply add it to the amalgamation of posts on the SNES CD thread.

 

Hm, ok. Cool.

 

You get an A+ for vocabulary.
The owners of this console should go visit Kevtris and have him figure it out.

 

I don't have any interest in the value of the thing as a collectible item but I really hope it gets dumped so I can look at the ROM, mostly out of curiosity.

Given that it has a fully functioning SNES mainboard, and just going by the part numbers on the chips, I would venture to guess that this was mostly to determine the feasibility of using a CD to deliver content to the existing SNES architecture in lieu of a cartridge, rather than a radically new design. Dumping the cartridge ROM would be a great place to start.

What may be present however is some early iteration of the CD-XA stuff that went into the Playstation MDEC for full motion video playback. If so, it would be neat to see how they implemented the new video modes on top of the (or through) the existing SNES video hardware.

 

The fact that it seemed so similar to the SNES/Super Famicom in the way it functioned is what made me so skeptical in the first place, but seeing the other stuff got my excited. The cartridge is apparently stuff used for debugging and testing, so it really pisses me off that they didn't bother showing that in the video. It's like they just assumed all people would care about is "CAN IT PLAY GAMES AND SHIT", which I guess is true to some extent.

 

On the cart there is a Hitachi chip with a sticker labeled "0.95 SX" on it. Do we have a clue yet what that chip is? Everyone has been saying its a ROM chip of some sort but do we have the proof that it is? Could it be an MCU of some sort (a look at the cart picture shows a lot of traces comming from the SONY SRAM above the "0.95 SX" chip that seem to go to the socket for that "0.95 SX" chip and possibly connect to it which would make sense if it was an MCU with inbuilt ROM (which might then need external RAM to do its job).

Its quite likely the cartridge is acting as a "BIOS" for the CD where the ROM or MCU was responsible for reading the CD and feeding code/data into some RAM where the SNES 65816 could see it (which would explain the big WRAM chips on the board). Its also possible that there is extra graphics functionality in the system along the lines of what the FX chip and SA-1 did by giving you a raw frame buffer and a way to feed that to the SNES PPU. (and maybe part of the cartridge WRAM is dedicated to holding that frame buffer). It wouldn't surprise me if there is some sort of DMA going on where data transfer between the CD logic and WRAM is handled by the cartridge hardware (that MCU if it is one) leaving the SNES 65816 free to run main game code.

My educated guess is that the stuff marked "CD" is basically the same as the controller board from one of the Sony CD drives of the era and that it exposes certain registers to spots in the SNES memory map where the "BIOS" can talk to them and read data

Just throwing some theories out there based on my knowledge of electronics, my knowledge of SNES hardware and my experience with the 65816 CPU (I wrote some ASM hacks for Super Mario World back in the day

 

It doesn't seem to have anything like that - based on the on photos that have been posted, the main board has the same parts as a Super Famicom, but with 7 additional chips:

1) CXD2500 CD-DSP
2) CXD1800 CD-ROM decoder/interface
3) 32K SRAM (presuambly the CD-ROM sector buffer)
4) some 20 pin SOP device that looks like a bus buffer
5) a QFP with no markings (mechacon MCU?)
6) A Sanyo 16 bit stereo DAC
7) an 8 pin SOP - probably a dual opamp (it's next to the DAC outputs, so probably a buffer)

The top board has a 4-bit MCU and a liquid crystal display.

There are also 5 visible ICs on the back of the CD-ROM control board - one of them is a Rohm BTL driver another looks like a Sony CXA1272 (old CD drive focus / tracking servo) - the other chips are small SOP devices with numbers I can't read. No sign of an RF amp chip, but on a lot of those older drives it was built into the optical pickup. Basically, it has all the chips you would expect for a basic data/audio CD drive of that vintage and nothing else.

 

Yes but keeping all news in one place would be better.

 

But can't you see where I'm coming from? What would be really awesome is if the pre-existing thread could be stickied on the home page, it's a discussion that could make people create accounts to participate in.

 

All this does is create two different discussions about the same topic.

 

Feeling a little entitled, are we? They have an expo ahead of them, you'd think that they'd leave something, anything at all, for later? Nevermind the fact that it's their's and they can do what they want with it. That includes showing as much or as little as they want. I'm happy I got to see this much before the expo.

 

Excuse me? Did I come off as entitled? Oh, I'm sorry, I thought that people would agree with me on the fact that one of the most important items in gaming history should have proper video documentation covering all its aspects.

 

Yes, entitled.

 

Since the system does nothing when you don't put a cartridge and I don't see any kind of ROM on the system PCB, AND the fact that "0.95" appears on the Self-Check test, for me that "0.95 SX" chip is just the BIOS ROM.

 

Awesome, muted.

 

You just have no patience and you're way too hyped about this than what is healthy for a human being. Then you're trying to mask your lack of patience and your entitledness by talking high and mighty about "preservation". Yeah, right. It's been said a trillion hundred times by the guy and his dad that they'll do everything to preserve it as much as possible, so instead of bsing you could've just said "oops my bad, I actually don't have a right to be pissed off by the fact that they didn't film their every breath for my sake". You know what pisses me off? People who feel they are intitled to other people's things and who keep bsing. Jesus.