C128cr

gazcbm · February 19, 2009, 02:24 AM

Hi All,

I have just picked up a C128 mainboard that appears to be the same type as Ray Carlsens engineering board http://www.cbmhardware.de/c128/schematics/c128cr.jpg.

It has the kernal roms missing and no VIC /VDIC so havent been able to test whether its working.

I have read a few articles that suggest this never entered mass production and was also never released in europe, but I wonder how accurate this is? Does anyone have any further information about these boards?

Thanks
Gazcbm

SmallCleverDinosaur · February 19, 2009, 06:41 AM

This is a very rare item you've picked up

Probably one of the few that exists.

This actually comes from a "flat" C128 and not a C128D (or C128DCR)?

airship · February 19, 2009, 07:13 AM

I don't know if that version of the ROM images is available for burning or not. You could probably find the proper ceramic VIC chip if you hunt around a bit.

gazcbm · February 19, 2009, 09:13 AM

:-) Yay at last a bit of luck on my side!!

It is definitely from a C128 flat because it came from a flat style case which I am sure also reads C128cr alongside the serial (I will check this to confirm). The main board also has more model information on the silkscreen (Fabrication Number and Revision), I will post all the info and pictures this weekend so you can take a look.

Now I know a little more about this, I am very keen to getting it up and running. Airship, do you know of anywhere (other than ebay) where I may be able to find the ceramics?

RobertB · February 19, 2009, 09:56 AM

Quote from: airship on February 19, 2009, 07:13 AMI don't know if that version of the ROM images is available for burning or not.

When Jeri Ellsworth, Peter Hanson, and I visited former CBM dealer/repairman Jim Scabery in Portland, Oregon in 2007, Jim gave Jeri some C128 ceramic kernal chips that he had saved. She had never known those uncommon revisions before.

Truly,
Robert Bernardo
Fresno Commodore User Group
http://videocam.net.au/fcug
CommVEx v5 info -- http://www.commodore.ca/forum and click on ComVEX

SmallCleverDinosaur · February 19, 2009, 05:05 PM

But even though this is a C128cr it should be possible to use kernal ROM's from an ordinary C128, wouldn't it? There might be some functional differences in the ROM revisions, but there shouldn't be such differences that the computer won't function properly. The surrounding and supporting chips are still the same as in an ordinary C128.

airship · February 20, 2009, 01:42 AM

Quote from: SmallCleverDinosaur on February 19, 2009, 05:05 PM
But even though this is a C128cr it should be possible to use kernal ROM's from an ordinary C128, wouldn't it? There might be some functional differences in the ROM revisions, but there shouldn't be such differences that the computer won't function properly. The surrounding and supporting chips are still the same as in an ordinary C128.

Probably. I was just thinking that for something as apparently rare as this, he'd want to do an historically accurate restoration on it.

gazcbm · February 20, 2009, 11:49 PM

I would certainly like to restore it to as orignial as possible with ceramic chips if available.

Also I checked my cases and none have c128cr written on them, problem is when I removed the mainboard I didnt realise its importance and the case could now be one of 4 :-( There are 2 German cases, 1 English and 1 Hong Kong, I will try to work it out, but I guess they may not be original anyway.

I have attached a picture of the board for you to take a look, I have never seen a c128dcr board so who knows this could one of them.

SmallCleverDinosaur · February 21, 2009, 12:52 AM

This is definitely a C128cr board

You can tell from the yellow label on the expansion port as well as the dark text written vertically on the left side of the board.

But most important of all, the CR's uses 41256x4 memory circuits instead of 4164x1 for their RAM. By doing that you only need 4 IC's for 128KB of RAM instead of 16. If you take a look at your scan you'll find these circuits a little to the left below the expansion port connector. They are labeled (on the pcb) U38, U39, U40 and U41.

wfking · February 26, 2009, 10:38 PM

To find the correct case, you should check the positions of the screws. The -CR board is smaller and therefore some screw holes are different.

wfking · March 02, 2009, 01:17 AM

Quote from: gazcbm on February 20, 2009, 11:49 PM
I would certainly like to restore it to as orignial as possible

Then you should remove the 6581 SID and insert a 8580 SID.

gazcbm · June 05, 2009, 09:03 AM

I have been looking around for more information on this and have found somebody else with a similar board.

http://www.forum64.de/wbb3/index.php?page=Thread&threadID=20603&pageNo=1

C128cr

wfking

wfking