On Thursday 16 July 2015, 01:34:50 Bo Zimmerman <email@example.com> 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? -- http://www.hitmen-console.org http://magicdisk.untergrund.net http://www.pokefinder.org http://ar.pokefinder.org Die [weiber] wollen entweder a) ficken oder b) sich darüber beschweren, dass männer nur ans ficken denken <Graham/Oxyron> Message was sent through the cbm-hackers mailing listReceived on 2015-07-16 09:00:07
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