Re: 128CR (fwd)

From: Nicolas Welte (
Date: 2000-01-26 17:42:11

Hello Ray!

>      The board I have is a flat 128CR. I actually ordered a 128DCR board
> from Grapevine before they went belly up and got this one by mistake. Hey,
> at least it works! The ROM dump Marko mentioned came from this board, a
> C128CR Rev 3 PCB# 252270 PCB Assy# 250783. It is the same size but has a
> different layout than the standard 128. Some differences I noticed... On a
> paper sticker: "C128CR #2 ENG SAMPLE Jun/9/86 KNT". The RGB chip at U22 is
> a 2568R1X instead of the 8563 normally used.

According to the C128/C128D service manual (which Marko just put into
the funet filesystem) the 2568 is the same as the 8568, except it
expects the clock input at CMOS levels, not at TTL levels like the 8568.
It's _really_ amazing that this chip exists at all, I didn't even dare
to dream of one showing up. So my guess that the 128CR uses a 8568 like
the 128DCR wasn't that wrong after all :-)

> It has two 8701 chips (U28 [or
> is it U24] and U42) and a second crystal. The two ROMs (both 27256 EPROMS)

Can you read what is printed onto the crystals? What type of crystal is
it, a simple two pin crystal or a four pin oscillator package? Is there
still a separate 16MHz oscillator package for the VDC chip or maybe one
8701 is used to generate the 16MHz VDC clock?

> at U32 and U34 (U36 empty socket) are in the center of the board (not at
> the left end as in standard 128) and the video box is at the left side of
> the board. VRAM is 4416 chips and DRAM is 4464 X 4 @ U38 to U41. Other than

This must be the only machine which uses a ?568 VDC and only 16k of
video RAM. Damn, so my guess was wrong on this detail ;-)

> the above, the chips appear to be the same as the standard 128. If you need
> further info on that board, feel free to email me. Be specific in your
> questions, by the way. I'm just a lowly repair tech, not really a hacker.

But you're the most helpful and knowledgeful repair tech we have around

> :) I'm trying to think of the best way to get a photo of this beast. It's
> too big for my scanner. ;-)

Maybe it can be scanned in two parts? 

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