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Chip degradation

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Chip degradation

by lizardb0y » Sun Oct 09, 2011 8:12 am

I saw this post on comp.sys.cbm this morning. I've seen a couple of ROMs seen to become corrupt in use over the past 2 or 3 years. Is anyone else noticing this?


---------- Forwarded message ----------
From: "Clocky" <notg...@happen.com>
Date: Oct 8, 9:14 pm
Subject: First DRAM, now recurring mask ROM failures.
To: comp.sys.cbm


As most of you know I like to repair old computers and of late a lot of
failures have been due to faulty DRAM. In the most recent years I've noticed
that mask ROMs are also losing their data. Just this week I had a Panasonic
JR-200U fired up. I entered a small BASIC program that repeats and ran it.

After a minute or so the program locked up. Restarting the computer dumped
me into the built-in monitor. I suspected a ROM problem because BASIC is on
one ROM and the monitor on the other.

Desoldering the ROMs, dumping them and comparing them with Winhex to known
good dumps found online confirmed that the BASIC ROM had scrambled itself
and was completely destroyed. That it happened whilst the computer was on
and running is quite unusual.

Burning a fresh copy onto EPROM fixed it :-). I've noticed that cartridges
and ROM's in old computers from the early 80's seem to be dying, perhaps
reaching their design limitations for data retention and that is of some
concern particularly for more obscure systems.

Has anyone else noticed this phenomenon though?
lizardb0y / Andrew
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Re: Chip degradation

by Carcenomy » Sun Oct 09, 2011 1:09 pm

Yeap. The old MOS ROM chips in CBM machines seem to be starting to die, luckily stocks of replacements are still good.
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Re: Chip degradation

by tezza » Sun Oct 09, 2011 3:16 pm

Oh yes, I've had plenty of examples of dead mask ROMS. System 80, Sorcerer, Commodore PET. Aging no doubt but it would be interesting to know the exact process.
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