[Coco] CoCo 1 vs 2 detection (was 86-87 GIME chip detect challenge)

[John Kowalski]

Darren A wrote:

>I think I may have found a way to detect a CoCo1 vs a CoCo2. At least it
>worked in the very limited test of the two machines I have. Rather than
>look for the SALT chip it tries to detect if the machine has the custom
>integrated DAC chip.
>
>The theory is that the custom chip in the CoCo 2 does not allow
>bidirectional flow through the analog switch, whereas the MC14529B used in
>the CoCo 1 does. The test selects the cassette port as the audio source
>and then toggles the single-bit sound output while looking for a change on
>the cassette data input. If the predicted change is seen then it would
>appear that bidirectional flow through the switch is occuring and the
>machine is a CoCo 1.

That sounds like a brilliant idea.
Another possibility might be in reading the joystick ports - The delay
time before getting a valid reading from the comparitor after feeding
the DAC a value and switching to joy 0 input from sound output is
probably slower on a CoCo 1.

-- 
John Kowalski / Sock Master
http://users.aei.ca/twilight/sock