Re: The C128 Keyboard IO controller is...

Date: Thu, 16 Jul 2015 10:38:34 +0200
Message-ID: <2951690.CgGXZg7s1T@rakete>
On Thursday 16 July 2015, 01:34:50 Bo Zimmerman <> wrote:
> I often hesitate to post my personal discoveries to this list, fearing I
> will say something obvious, like "Hey guys! Did you know that if you
> remove the 6581 chip, the C64 stops making sound????"
> However, this is strange enough that I will take a chance.
> Hey guys! Did you know that it appears like a different CIA chip handles
> keyboard signals, depending on whether or not the Z80 is operating?
> I boot CP/M on my flat C128 rather often, and one day I booted into it
> to discover that the keyboard no longer worked.  The keyboard worked
> fine in regular c64 and c128 mode.   I was also seeing strange
> intermittant behavior on the IEC bus at the same time.  I decided it
> must be a twitchy CIA.  Thank the Makers that both the CIAs in the flat
> C128 are socketed.  I simply swapped them, which should take care of bad
> CIA and poorly seated chip problems.  Well, to my surprise, when I
> booted it next, the keyboard worked fine in CP/M, and did not work at
> all in c64/c128 modes.  I then replaced the bad CIA (it was the one
> closest to the user port), and everything is good.
> I'm perusing the schematic, and it makes no sense to me.  But there it is.
> I apologize if this is common knowledge, but it surprised the heck out
> of me.

perhaps CP/M scans the keyboard in a different way, which doesnt work on a 
partially broken CIA?


Die [weiber] wollen entweder a) ficken oder b) sich darüber beschweren, dass 
männer nur ans ficken denken 

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Received on 2015-07-16 09:00:07

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