[vcf-midatlantic] Need Yamaha C1 EPROM images

[Jonathan Gevaryahu]

On 12/15/2015 10:23 AM, Ethan via vcf-midatlantic wrote:
> Longshot but looking for the bios and 3rd chip EPROM images from the 
> Yamaha C1 286-10 "music" laptop.
>
> I posted the floppy disk dumps that are pack in including some 
> developer dox (including pinout of expansion connector!) in both disk 
> image and zip format online. I also posted the EPROM dumps that I have 
> -- I noticed text from the Copyright notices is corrupted so I'm 
> thinking my issue with the computer is the eproms are going bad. There 
> sems to be a lot of flaky/dead units out there (when I can find them.) 
> I think the machine is strange enough not to be able to use other 
> generic bios copies.
>
> Link of floppy files and my (prob bad) bios dumps:
> https://users.757.org/~ethan/pics/geek/Software/Yamaha_C1_Laptop/
>
>
>
Looked at the roms:
IC62 is a character set rom.
It contains (from analysis with Neil Corlett's NanaWin):
0x0000-0x07ff: Character set, 8x8, one character per 8 bytes, top to 
bottom of character; 000-127 is normal IBM codepage 437 characters, 
128-255 is a non-codepage 437 graphical set
0x0800-0x0fff: Blank.
0x1000-0x17ff: Top half of an 8x16 (or 8x12 or 8x14, unclear) font, same 
character set as above, i.e. 'half codepage 437, half graphical'.
0x1800-0x1fff: Bottom half of the 8x16 (8x12 or 8x14 of that is used) 
font at 0x1000-0x17ff
0x2000-0x27ff: Character set, 8x8, one character per 8 bytes, top to 
bottom of character; All 256 characters are the standard IBM codepage 
437 characters.
0x2800-0x2fff: Blank.
0x3000-0x37ff: Top half of an 8x16 (or 8x12 or 8x14, unclear) font, 
codepage 437
0x3800-0x3fff: Bottom half of the 8x16 (8x12 or 8x14 of that is used) 
font at 0x3000-0x37ff
0x4000-0x5fff: same as 0x2000-3fff
0x6000-0x7fff: same as 0x2000-3fff


The other two roms are supposed to be interleaved; IC39 is EVEN and IC40 
is ODD. (so the cpu must be 16 bits wide like 8086 and 80286, and the 
rom likely lives at 0xf0000-0xfffff as on any ibm-compatible PC)
Other than the first byte of each rom being weird (you'd expect them 
both to be 0x43 0x43 to make the copyright message work, but they're 
0x50 and 0x9a, which may have been intentional to make some sort of ROM 
Checksum work) they look pretty normal, I didn't see any obvious corruption.

Do they read out consistently?

-- 
Jonathan Gevaryahu
jgevaryahu at gmail.com
jgevaryahu at hotmail.com