Re: partial CIA #2 failure?

From: Marko Mäkelä (
Date: 2006-08-31 08:04:58

On Wed, Aug 30, 2006 at 08:36:57PM -0700, Cameron Kaiser wrote:
> Anyone seen a *partial* failure of CIA #2? Serial bus (including 128 mode
> fast serial) and VIC banking all work normally, but user port communications
> are busted (tried two different interfaces and terminal programs; hooked the
> UDS-10 up to a Turbo232 and in that circumstance everything *does* work).
> This is in a 128DCR; I haven't cracked the unit yet to examine the board.

I have experienced partial chip failure.  You can fry individual pins of
chips.  I once installed a cable between the user port of a Commodore 64
or 128 and the printer port of a IBM PC compatible.  I accidentally plugged
the user port connector upside down, and the PC (running GNU/Linux) crashed
the moment I powered on the Commodore.  The pin that got 9 volts AC obviously
was fried, but the remaining pins were okay.

Also, on a newer PC, I somehow managed to fry RTS and CTS on the serial port,
perhaps by using a wrongly built cable.  The TxD pin works.

> Suggestions appreciated.

Replace the CIA.


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