Re: CBM 610: FPLA Failure?

From: Marko Mäkelä (
Date: 1999-07-25 17:05:43

Hallo Marc,

On Sun, 25 Jul 1999 wrote:

> Gudday,
> congratutlations on your comprehensive collection of material on the computer 
> gems of the 1980's: Commodore's 600 & 700 Series. So far, I found everything 
> I needed here ;-).
> Unfortunately, my Commodore 610 (Serial #1466) seems to have deteriorated, by 
> aging, I suppose: strings stored in memory are not read properly, e.g. the 
> filename in load-commands is garbeled randomly with Pi-characters. These have 
> the memory code of 0xFF, so obviously the data bus read is hi-impedance or 
> the data is not stored and/or refreshed properly in the dynamic RAM 
> (Bank1&2). So I suspect the system-decoder-FPLA 82S100 (U18, Commodore 
> Part#906114) to be in doubtful condition. I plan to replace this by a PAL16L8 
> with adaptor socket - I have the logical equations, but am not sure if they 
> are correct. If you are interested, I might contribute these parts 
> (documented PAL and adaptor layout).
> I'd like to get your advice on this topic - do my observations make sense, or 
> is there another known bug in the system producing these symptoms? Ullrich 
> von Bassewitz suggested the video RAM might be affected, but I don't see how 
> that would affect stored strings.
> Best regards & greetings from Brunswick (Germany),
> Marc

I'm forwarding this to the cbm-hackers mailing list, since I don't know
anything about the 610 (except the documents that have been uploaded to

I don't think that it is the PLA.  If there is a data bus multiplexer, I'd
have a look at it first.  But of course, I'm interested in the PLA

BTW, is "Brunswick" the English spelling of "Braunschweig"?  That was
where the German headquarters of Commodore were located, right?


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