[Coco] CoCo-4?

[Paul T. Barton]

--- peak at mail.polarcomm.com wrote:
> Yes, you surmised correctly that I would not be
> running most 
> coco software as that would require keeping the
> GIME 
> chip,However I would like to build a coco2 like
> system and 
> might include a sam chip or two, but with the
> more advanced 
> features of later technology IE. Hi speed
> hitachi 6309, 2 or 
> more 43256 static ram chips (This would enable
> me to run the 
> computer at a higher speed by turning off the
> address 
> dependent speed and the slow speed). Then I
> could run in fast 
> speed only. If we are truly going to speed-up
> the machine we 
> need to run all of the computer at a higher
> speed>(not just the CPU)    
--snipped--
Actually the video is linked to the CPU speed.
If you build a "similar" system, don't forget
to  interleave the video accesses between
CPU accesses. This gives no video snow.
Years ago we did a circuit (schematics, yes)
that used the MC6847 interleaved without
the SAM chip. The MC6847 was "either" edge
triggered, but we got it to work and work
with a 6800 type CPU, first.

Paul T Barton


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