Re: BASIC for the CBM-II/8088

Hello!

Mia Magnusson wrote:

> I think it would be great to investigate how the 8284A and the 8088
> works cycle for cycle. By either replacing the 8284A with programmable
> logic, or using some of it's features currently not in use on the B
> 8088 card, it might be possible to sync the 8088 to the 6509 clocks.
> (And as I suggested earlier, run the 8088 at 18/3MHz instead of
> 15/3MHz).

How about using a V20? It uses a symmetrical clock, so it might be
easier to synchronize it with the 6509. It can also be clocked up to
20MHz, although I have no idea how the rest of the system would behave
in such case.

> Btw the P500 also has the BUSY1/2 mechanism, so the reason for the 8088
> board not working in that is probably some hardware bug somewhere, or
> maybe as simple as the dram on the P motherboard being too slow (as
> with the 6509 it is used at 1MHz instead of at 2MHz).
> Btw are we 100% sure that the 8088 card won't work in a P500?

I don't think anybody has ever tried using it on a P500 :-) It does not
work on the 610 due to differences on the mainboard, but P500? Nobody
knows at this point.

> As the 8088 seems a bit faster, maybe it's faster to do the petscii
> conversion on the 8088 side? This is something worth experimenting
> with. Both CPU's have known speeds but they aren't synced together, so
> it's a bit hard to do something like the fastloaders for C64+1541 which
> relies on two CPU's running at almost the same speed, making it
> possible to transfer data without handshaking all the time.

A 5 MHz 8088 is only marginally faster than a 2 MHz 6509 - according to
my rough calculations, by about 20-30% in such a task. And then, even
when it does the PETSCII conversion, it cannot access the video memory
so you need to engage the 6509 anyway to copy the converted data.

Regards,
Michau.