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SNES-CD technical specifications 
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Joined: Fri 10 Apr 2009, 15:00:08

Posts: 13668
Post SNES-CD technical specifications
Something I've never seen before. Unfortunately very little technical info. We get the RAM sizes, a note that the CD-decoder is a 6502 @ 4MHz with some bitmap conversion and sound table functions. And unfortunately no word on what the 32-bit RISC ISA would be.

https://docs.google.com/file/d/0B4cc2TZ ... dr/preview

Thoughts:
* only 1MB of RAM for the actual game to have available in the base cart. Would have enforced a lot more load screens.
* the CD case was going to contain SRAM ... no memory cards or internal memory management. If only Sony had done this.
* latency of ~1s to start an audio track. Can't read data during audio playback (no surprise.)

Fri 14 Feb 2014, 12:59:53

Joined: Wed 06 May 2009, 04:13:19

Posts: 4543
Post Re: SNES-CD technical specifications
byuu wrote:
Something I've never seen before. Unfortunately very little technical info. We get the RAM sizes, a note that the CD-decoder is a 6502 @ 4MHz with some bitmap conversion and sound table functions. And unfortunately no word on what the 32-bit RISC ISA would be.

https://docs.google.com/file/d/0B4cc2TZ ... dr/preview

Ooooooh...


Quote:
Thoughts:
* only 1MB of RAM for the actual game to have available in the base cart. Would have enforced a lot more load screens.

That's not... Oh, wait. Stupid case-sensitive bit/byte abbreviations.


Quote:
* the CD case was going to contain SRAM ... no memory cards or internal memory management. If only Sony had done this.

And a lockout chip. And CD writers weren't even widely available yet.

Though most everyone that wasn't Sony was building a good chunk of NVRAM into the console so memory cards were optional. Until people started dinging them for not using memory cards like the PlayStation did.
*sigh*
I hate people.

Quote:
* latency of ~1s to start an audio track. Can't read data during audio playback (no surprise.)

HOORAY REDBOOK!



And oh oh, I think I see where the "SNES CD was gonna be a CD-i unit" rumors came from.
There's a section where they explain what a compact disk is(ahhh, the 90s), and the different formats. And they explain that "With the exception of file structure, CD ROM XA is nearly identical to CD-i."
Not hard enough evidence to put the "CD-i module" rumor to rest, but I'd bet money that's where the rumor started.

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Fri 14 Feb 2014, 14:11:15

Joined: Tue 30 Jul 2013, 15:33:32

Posts: 27
Location: Silent Hell
Post Re: SNES-CD technical specifications
byuu wrote:


Excellent discovery, byuu. :D

byuu wrote:
And unfortunately no word on what the 32-bit RISC ISA would be.


I'd be willing to bet that it was either the R3000 or R2000.

The only evidence to support that, however, are the facts that

1: The Playstation uses the R3000
2: The R3000 used in the PSone utilizes 1Kbyte cache, the same as SNES-CD
3: That document is dated Feb of 1993, whereas the PSone launched just under two years later.
4: Executables are developed using C-compilers, same as the proposed SNES-CD.

However, the clock speed is much different, which leads me to think/hope/believe that it may have been the R2000. Further evidence to support the R2000 theory is the fact that Sony and Nintendo began conception of the SNES-CD in 1986, the same year the R2000 processor was released.

byuu wrote:
* only 1MB of RAM for the actual game to have available in the base cart. Would have enforced a lot more load screens.


Well, the PSone has exactly 2MB, so go figure. :P

Furthermore, the CD-drive for both the PSone and SNES-CD are pretty much the same, obviously excluding the SRAM add-on and protective case.



That said, if/when one of the "200 or so" SNES-CD machines that were produced gets sold to Assembler, etc., I wouldn't be surprised to discover that the SNES-CD is nothing more than a very early alpha version of Sony's Playstation.

Fri 14 Feb 2014, 17:01:01
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Joined: Tue 22 Dec 2009, 11:19:28

Posts: 280
Post Re: SNES-CD technical specifications
*instant download*

I saw this for a while, but I never knew it was actually scanned.
Too bad there's not much details to it.

But CD-ROM XA... damn. And CD-i specs. That's something.

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Fri 14 Feb 2014, 18:49:24
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Joined: Fri 10 Apr 2009, 18:17:56

Posts: 3308
Location: Germany
Post Re: SNES-CD technical specifications
CD-i core in higan when? :P

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Fri 14 Feb 2014, 19:00:24
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Joined: Tue 22 Dec 2009, 11:19:28

Posts: 280
Post Re: SNES-CD technical specifications
Byuu, make this Mario Factory core:
https://www.google.com/patents/US5599231

Unbelievably, it's very detailed.

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Deal with it.

Fri 14 Feb 2014, 20:14:04

Joined: Wed 06 May 2009, 04:13:19

Posts: 4543
Post Re: SNES-CD technical specifications
LuigiBlood wrote:
But CD-ROM XA... damn. And CD-i specs. That's something.

*bangs head*
There was nothing CD-i about the hardware. The only thing even remotely related to CD-i was CD XA's data formatting, which was imported from the Green Book.

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Sat 15 Feb 2014, 10:22:32
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Joined: Mon 20 Apr 2009, 08:11:50

Posts: 5266
Location: 日本
Post Re: SNES-CD technical specifications
This CaptainJistuce, he's an expert with all of those colored books. But he'll never be as cool as Jaybee.

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Sat 15 Feb 2014, 12:57:11

Joined: Wed 06 May 2009, 04:13:19

Posts: 4543
Post Re: SNES-CD technical specifications
Kakashi wrote:
This CaptainJistuce, he's an expert with all of those colored books. But he'll never be as cool as Jaybee.

Please. That Jaybee is just a stoned puppy dog that lays on the floor drooling all day.

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Sat 15 Feb 2014, 13:30:13

Joined: Sat 18 Apr 2009, 16:06:52

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Post Re: SNES-CD technical specifications
I have long held the viewpoint that the RISC processor in SNES CD was NEC V810. It has a 1KB instruction cache/no data cache (the SNES CD specs make it clear that the 1KB cache is for instructions or "commands"). This is the processor that Nintendo went on to use in the Virtual Boy, where it was clocked fairly close to the SNES CD specs (20MHz vs 21.477MHz) - it was also used in the NEC PC-FX where it was clocked at effectively the same rate (21.5MHz). Also, V810 had floating point as per the SNES CD specs, something that had to be added as a coprocessor on R3000, which PS1 for instance did not do.

The CPU in the PS1 actually has 4KB of instruction cache. It's the data scratchpad that's only 1KB large, and I'd like to stress that this isn't a cache.

Mon 17 Feb 2014, 06:08:02

Joined: Tue 30 Jul 2013, 15:33:32

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Location: Silent Hell
Post Re: SNES-CD technical specifications
Exophase wrote:
The CPU in the PS1 actually has 4KB of instruction cache. It's the data scratchpad that's only 1KB large, and I'd like to stress that this isn't a cache.


Yup, you're absolutely correct - it was my mistake to confuse the two.

Mon 17 Feb 2014, 17:12:29

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