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PostPosted: Sat Mar 17, 2018 9:02 pm 

Joined: Mon Aug 28, 2017 6:00 pm
Posts: 8
After getting a glimpse of the PCB photos from Ben Heckendorn's teardown of the system and some ideas from the analysis of the hardware by various individuals on here, I was convinced that the design of the hardware controlling the CD drive portion of the console could not have been too different from something that Sony, the mother of all things CD related, had not already produced.

I noticed one of the BIOS start-screens had a message reading “Electronic Book”, as if eBooks were on CDs at one point (they were). I became curious as to what that “Electronic Book” thing was. After doing some research, I discovered that Sony had made a portable eBook player that read books stored on 8cm CDs called the Sony Data Discman. The devices themselves sport a dot matrix display, QWERTY keyboard, and a Caddy CD drive for 8cm CDs. They are capable of playing music CDs, too.

Somewhere on this message board, individuals discovered that the CXD1800 chip used in the SNES CD shared identical registers to that of the CXD1196 IC (concluded from analyzing the BIOS test program and finding a data sheet on the CXD1196).

I decided to purchase several models of the Sony Data Discman on a hunch that, maybe, one of these would have similar and/or identical hardware to what is inside the SNES-CD. Upon inspection of several units, I noticed several of them contain a CXD2500 and CXD1196 (similar to the configuration used in the SNES-CD with the CXD2500 and CXD1800). I have included a photo of the PCB from the Sony DD-8. Almost every Sony DD is powered by a Z80 CPU, and similar supporting hardware. The one large ASIC on this PCB, the CXD8279R, is the glue logic for almost everything on this board. The service manuals calls this IC the “Extended I/O”. My speculation is that this is similar to that unmarked chip on the SNES-CD motherboard.

File comment: Sony DD-8 motherboard
DD8_labeled.jpg [ 1 MiB | Viewed 434 times ]

As far as the software on the Sony Data Discman is concerned - These devices do have a built in test feature which I found how to invoke looking through the service manuals. The test screens used have a strangely similar layout to that of the SNES-CD BIOS test screen (“Test name” ---- “OK/NG” (OK - test pass, NG - No Good/test failed).

I messaged nocash several months ago inquiring if the SNES-CD BIOS had any functionality to read these eBook CDs as I was not too familiar with the SNES-CD BIOS and don’t know too much about CD standards.

Thanks for nocash in help with pointing this out: The SNES-CD BIOS has some very basic functionality in reading eBooks from Sony Data Discman CDs, a "Hello World" equivalent of a program. The program reads the text data from the CD but doesn’t provide many of the fancy features the Sony DD does (searching for text, bookmarking chapters, playing audio from selecting an item in the UI, etc…).

File comment: A different textbook, it appears Hiragana, Katakana, and a few symbols mostly work.
textunkown.PNG [ 17.85 KiB | Viewed 434 times ]

File comment: Title screen upon first loading the CD. The top should read "この電子ブックは" - roughly "In this electronic book...". The Sony Data Discman units display this similar text on their "table of contents"/home screen. Selecting one of those options /should/ bring the user to a specific section on the CD. Doesn't appear to do much in this BIOS demo.
Title Screen.PNG
Title Screen.PNG [ 5.72 KiB | Viewed 434 times ]

Unfortunately, most of what can be displayed is garbage as the program is trying to access character data (Kanji characters, symbols, other graphics?) that is outside of the ROMs memory space (thanks again to nocash for this analysis). As a result, there is speculation the program was still in development or hastily thrown together, or the ROM was not fully dumped (This I do not know).

I feel this is worth bringing up due to similarities in the hardware and basic software functionality to support reading these eBook CDs.

PostPosted: Sat Mar 17, 2018 9:31 pm 

Joined: Sun Apr 13, 2008 11:12 am
Posts: 6924
Location: Seattle
That's really cool! Thanks for sharing!

PostPosted: Sun Mar 18, 2018 12:22 pm 

Joined: Fri Feb 24, 2012 12:09 pm
Posts: 555
Good that you've put that online! I was wondering if we should share the discovered info after exchanging those PMs months ago.

From what I remember, the snes electronic book support was quite limited. It's barely supporting the main menu and text pages linked from that menu (but not sub-menues or other special features like entering search terms in dictionaries). The font doesn't have all characters defined (despite of having some support for loading custom symbols to RAM) (the missing characters would be located at higher ROM addresses, ie. the existing bios dump is somewhat incomplete - either because it wasn't dumped properly, or because the cart did actually contain a chip that was too small). Text can consist of 8bit or 16bit character numbers, and narrow 8x16pix and wide 16x16pix characters (with only either one supported in some cases). And the cdrom loading is limited to reading only a few kbytes per document (longer chapters are simply cropped to that size).

To get it working one would need to patch the disc detection in the snes-cd bios:
0000:81A7 20 2D 86     call 862D  ----> check volume descriptor  ;out: A=00h/FFh
0000:81AA 30 3F        js   @@not_super_disc
0000:81AC D0 64        jnz  @@electronic_book    <--- CAN'T HAPPEN

eg. replace the "30 3F" (=jump if signed) at address 81AAh by "EA EA" (=two nops), with that change it should still accept snes/game discs, and treat anything else as electronic book, this should also work in no$sns (if you have an electronic book disc image). But don't expect anything better than remotely recognizeable gibberish (like what you've seen in DaveyPocket's screenshots above). If I remember correctly, the Langenscheidt's discs had some working english/german text appearing in the menu - but didn't work when clicking menu items).

It's been quite interesting to see that hidden feature in the snes-cd, although it's rather nonfunctional. I guess the devr's have just used it for testing if they could "read a few text strings from the disc", ie. something done during early testing, at a time when game discs didn't even exist yet... or maybe they had planned to extend the feature at some point in future, adding support for actually viewing longer documents in different formats... allowing people to view electronics dictionaries in the living rooms, which, I guess it would have been pure sci-fi, at least if it would have happened a few years earlier in the 80's.

Oh, and the ebook discs were encapsulated in cartridges, so one would need to disassemble the cartridge before inserting the raw disc into the snes cdrom tray. Davey said that it's relatively easy to do so, but I think it wouldn't be the optional user experience... having all that brandnew modern hitec equipment - and then needing to use your teeth or fingernails to get it working ; )

Last edited by nocash on Sun Mar 18, 2018 12:44 pm, edited 3 times in total.

PostPosted: Sun Mar 18, 2018 12:30 pm 
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Joined: Mon Jan 23, 2006 7:47 am
Posts: 89
So the SNES-CD / Play Station timeline looks probably like this:

1958 to 1969 - VIDEODISK: transparent analog disc (incl. 2 analog audio tracks) by David Paul Gregg
1965 to 1969 - stationary transparent digital disc by James Russell
1970-01 - Unix time begins
1971-?? - Intel 4004
1972-?? - Intel 8008
1972-09 - Magnavox Odyssey
1974-03 - Motorola 6800
1974-04 - Intel 8080
1975-04 - Vietnam War ends
1975-09 - MOS 6502
1976-03 - Zilog Z80
1976-04 - Apple I
1977-06 - Apple II
1977-09 - Atari 2600
1977-10 - Commodore PET
1978-12 - LaserDisc by MCA, Philips, Pioneer: analog video, analog FM stereo sound and PCM digital audio
1978-06 - Intel 8086
1979-07 - Sony TPS-L2: mobile "Walkman" cassette player
1979-09 - Motorola 68000
1979-11 - Atari 400 / 800
1980-04 - Nintendo Game & Watch
1981-06 - LaserDisc release in Japan
1981-08 - IBM PC
1982-08 - Commodore 64
1982-08 - Compact disk by Philips, Sony
1982-10 - Sony CDP-101: stationary CD player; mass production of CDs begins
1982-11 - Atari 5200
1983-09 - North-American Video Game Crash
1983-07 - Nintendo Famicom
1983-07 - SEGA SG-1000
1984-03 - WDC 65c816
1984-11 - Sony D-50: portable "Discman" CD player
1985-06 - Atari ST
1985-07 - Commodore Amiga
1985-10 - SEGA Mark III / Master System
1985-10 - North-American Video Game Crash ends with the NES released in North America
1986-02 - Nintendo Famicom Disk System
1986-05 - Atari 7800
1987-?? - CD Video by Panasonic, Philips, Samsung, Sony (5min analog video and 20min digital audio)
1987-10 - PC Engine / TurboGrafx-16 by Hudson Soft and NEC, using CDs with hardware add-on unit
1988-10 - SEGA Genesis / SEGA Mega Drive
1988-?? - SPC700 development between Nintendo and Sony's Ken Kutaragi
1988-?? - development of SNES-CD (SNES CD addon) / Play Station (console for SNES carts and CDs) starts after the SPC700 is completed
1989-04 - Nintendo GameBoy
1989-09 - Atari Lynx
1990-04 - SNK Neo・Geo
1990-07 - Sony DD-1EX: ebook reader using 8cm (3.15") CDs
1990-10 - SEGA Game Gear
1990-11 - Nintendo SNES
1990-12 - NEC PC Engine GT / TurboExpress
1991-03 - Commodore CDTV, using CDs
1991-06 - Sony presents the Play Station; Nintendo reveals its partnership with Philips at the CES Las Vegas
1991-10 - Philips CD-i, using CDs
1991-12 - SEGA CD / SEGA Mega-CD, using CDs
1992-10 - 200-300 SNES-CD / Play Station prototypes have been created; Nintendo forces a new deal, retaining control and profit over the games
1993-?? - Sony cancels the deal with Nintendo, removes SNES features and changes the name to PlayStation
1993-?? - Sony CD-i Intelligent Discman, a portable CD-i unit
1993-10 - 3DO (by 3DO Company, Panasonic, Sanyo, GoldStar), using CDs
1993-11 - Atari Jaguar, using CDs with a hardware add-on
1994-11 - SEGA 32X
1994-11 - SEGA Saturn, using CDs
1994-12 - Sony PlayStation, using CDs
1994-12 - NEC PC-FX, using CDs
1995-10 - SEGA Nomad
1996-?? - Game Boy Pocket
1996-06 - Nintendo 64
1996-10 - Digital Versatile Disc by Sony and Philips
1997-10 - Gunpei Yokoi dies
1998-10 - Game Boy Color
1998-11 - SEGA Dreamcast, using Yamaha GD-ROM discs
1999-03 - SNK Neo Geo Pocket Color
1999-12 - Nintendo 64DD: magnetic disk drive peripheral for the Nintendo 64
2000-03 - Sony PlayStation 2, using DVDs
2001-03 - Game Boy Advance
2001-09 - Nintendo GameCube, using GameCube Game Discs by Panasonic

So the Sony Data Discman could very well have been a side project derived from the SNES-CD development, but still released almost one year before that fateful '91 CES.
_ _ _

Ironically enough there was also a portable CD-i unit, produced by... Sony. ... man.21183/ ... /102662474

Last edited by creaothceann on Mon Mar 19, 2018 3:14 am, edited 2 times in total.

PostPosted: Sun Mar 18, 2018 4:27 pm 

Joined: Fri Jun 26, 2009 4:58 pm
Posts: 106
creaothceann wrote:
1978-12 - LaserDisc by MCA, Philips, Pioneer: analog video, analog FM stereo sound and PCM digital audio

Crucially, digital audio wasn't introduced to LaserDisc until 1985, based on the already-released CD audio format, which itself built upon the design of LaserDisc.

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