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.
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…).
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.
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.
Attachment:
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…).
Attachment:
File comment: A different textbook, it appears Hiragana, Katakana, and a few symbols mostly work.
textunkown.PNG [ 17.85 KiB | Viewed 3149 times ]
textunkown.PNG [ 17.85 KiB | Viewed 3149 times ]
Attachment:
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 [ 5.72 KiB | Viewed 3149 times ]
Title Screen.PNG [ 5.72 KiB | Viewed 3149 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.