[vcf-midatlantic] Need Yamaha C1 EPROM images

[Ethan]

> 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

Ah interesting, I didn't try to look at them graphically, my tool of 
choice there is a Java app called "Tile Molester."

> 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.

I get that they were intereleaved, and I even wrote out a new set that had 
the wrong character corrected with no go.

> Do they read out consistently?

I've verified them a few times and it was fine. I could see activity on 
the data pins on the chips hitting some of the data and address lines on a 
scope, so there is some acitivity but it's my guess it's stuck in a loop 
or something.

The machine has a dip switch that switches the video between external 
(Herculeas or CGA) or internal LCD. No matter the position of the dip 
switch it's always coming up external, and I traced back the dip switch 
and it's read by software I think.

It had leaky caps -- I repleaced those and cleaned up the board. There 
could still be damage, but things look and test ok. When I've seen them up 
for sale 3/4ths of them seem to have the same always external 
video/nothing comes up issue.

 			- Ethan