> On 2018-06-12, at 23:02, Mia Magnusson <mia@plea.se> wrote: > >>>>>> I can't remember which versions, but at least some version of >>>>>> the CIAs can only be used as one of the two CIA's in a C64. >>>>>> Using it as the other CIA causes keyboard problems. >>>>> >>>>> no, both can be (and are commonly) used in either position >>>> >>>> Well, there are some revision of the CIA that only work in one >>>> position. I'll have to check the exact label of it. >>> >>> You sure you're not talking about using a 8520, meaning a CIA meant >>> for the Amiga, in a C64? >> >> i'm suspecting that too... and then it will only "kindof work" for >> some programs - anything complex will likely fail due to slightly >> different behaviour. > > I had a chat with the person who's been testing various CIA's. > > He claims that on a 250466 C64 board, the 8521 won't work in position > U1 while it works in U2. > > (I'm 100% sure he knows how to test it throughly, for example with > diagnostic cartridge and the right harness). > > If anyone else has a C64 with a 8521 as U2 and a 6526 as U1, it would > be nice if they could try swapping them. > > My guess is that some revisions of the 8521 uses output drivers which > drives hard enough in both directions so the keyboard scanning won't > work with some combinations of more than one key pressed. 250466 is my favourite board and I tested many CIAs with it. Never had any problems except the IRQ being flagged as faulty by the diagnostic cart we spoke about. -- SD! - http://e4aws.silverdr.com/Received on 2018-06-14 00:01:45
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