Re: Questions about 8563 and 8568

Den Sun, 24 Mar 2019 02:30:39 +0100 skrev Michał Pleban
<lists@michau.name>:
> Hello!
> 
> I cannot find the datasheets for 8563 and 8658 chips anywhere online.
> Are they available?
> 
> I am thinking about creating a graphics card with these chips for the
> CBM-II line, and I am looking for pertinent information. So far, I was
> not able to find answers to these questions:

Some kind of guesses:
 
> * What is the purpose of the CCLK pin, which is unconnected in both
> C128 and C12DCR?

Hook up an oscilloscope and check yourself!

It might be a "color clock" intended for composite generation, and if
so it would most likely need a suitable clock frequency that's some kind
of multiple of the color frequency.

> * The 8568 is said to have an output indicating that it has completed
> the operation, which is unused in the C128DCR. Would it be the pin
> number 8, which is unconnected and without description on the
> schematic?

Again, hook up an oscilloscope and see if something happens on that
pin :)

> * Would it be possible to run the chip at 18 MHz instead of 16 MHz as
> in the C128, and what are the possible consequences of doing so?

12.5% higher clock frequency, I'd say that there is a fairly good
chance for it to work.

Maybe you could change the frequency of a C128 and see if that seems to
work? Both a C128 and the B series runs the CPU bus at 2MHz, so that is
really something you'd like to try anyways.


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