Re: Broken P500

From: Michał Pleban <>
Date: Tue, 02 Oct 2012 21:36:24 +0200
Message-ID: <>

Rob Clarke wrote:

> WRT to the 6525, a bad one can 'black screen' the system. The one that
> handles the keyboard also controls the 16k bank that the vic-ii sees.
> When I got that batch of 6525's a few months ago I did not have a
> socketed 6525 in any of my cbm-ii machines to test with but I now have a
> P500 with a socketed 6525 and I know that some of the bad ones will stop
> the machine from visibly booting.

OK, that's indeed a valid theory. But I recall from previous
conversations from Steve that the activity on the address lines was
somewhat different from a working one, which a bad 6525 would not produce.

But this should be rather simple to check? One could just check the
voltage on these A14 and A15 pins coming out of the TPI?


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Received on 2012-10-02 20:00:38

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