[Coco] overdrive ...

[Kevin Diggs]

Hi,

jdaggett at gate.net wrote:
> Kevin
> 
> Exchanging data between the data bus sof the 6809 and the 68000 
> will need other than just syncing clocks. You would need some 
> bridge circuit that would allow the two data busses to be isolated yet 
> allow either to send data across. This is essentially what the PC 
> clones do in the north bridge and sout bridge chip sets. Logic that 
> allows data to flow from one data buss to another data buss. 
> 
> A simple bridge would be a dual port ram. This will allow either CPU 
> to pass data between the two data busses. There also needs to be a 
> protocol for exchange of data. 
> 
> james
> 

	I know you can't just hook them together, but wouldn't the design of 
the interface/bridge be simplified if you did not have to deal with the 
two clocks being asynchronous?

	A dual port ram would chew up lots of addresses on both sides, right? 
Could some kind of FIFO thing be used that would use minimal addresses 
on the coco/6809 side? Don't really care about the 68k side. One of the 
alternate address spaces could be used.

	Didn't the plcc (or other square/non-dip) version of the 68008 address 4M?

					kevin
					kevin