[Coco] CoCoRX

[Robert Gault]

Frank Pittel wrote:
> Sorry for responding so late but I got behind in reading email.
>
> Isn't the idea of the cartridge to test actual cocos? Unless seriously broken
> in ways I can't imagine possible a 6809 or 6309 is always going to clock cycle
> accurate. In the case of an emulator running on a PC or FPGA it should be up
> to the author(s) to indicate if it's clock cycle accurate. It's well known that
> the "cpu" on the coco3fpga isn't cycle accurate and neither will anything based
> on that core.
>
> The Other Frank
>
>
>
> On Sat, May 30, 2015 at 02:43:25PM -0500, Melanie and John Mark Mobley wrote:
>> We need a diagnostic test that will prove out the cycle accuracy timing of
>> the CPU so that it can be used to test the FPGA design.
>>
>> John Mark Mobley

To add a comment on this request, it would be impossible for any software to 
verify a "clock cycle" as it would run using the clock cycle in question. Unless 
the PAK contained its own crystal and timing circuits, there would not be any 
basis for measuring the Coco or emulator timing. If the PAK did include a clock 
circuit, how would that timing be verified?

Perhaps if the PAK included a realtime clock, the crystal in the clock could be 
used to validate the Coco/emulator timing by measuring the number of software 
loop cycles per some unit time. I have doubts about the precision of such 
measurements and the added cost to the PAK would probably be prohibitive.

A high precision counter would be needed to measure the Coco/emulator at various 
test points and the counter would need to be certified as to its accuracy to 
provide meaningful results.
Better just to assume if the unit under question produces reasonable pictures on 
a monitor, the timing is adequate.

Robert