[Coco] Detecting CoCo 1 versus CoCo 2

[johnmarkmelanie at gmail.com]

Jim,

I think John Linville made Firefall for the CoCo 2 because of a special simigraphics mode in the CoCo 2.

The high-speed poke may work better in the CoCo 2. Because of better grade parts with higher speed.

RAM refresh may work better in CoCo 2 during the high-speed poke.

The speed of the OP-AMP used in serial communications may be faster on the CoCo 2.

I wonder if the DAC and comparators used for the joystick can be used to detect a timing difference.

Perhaps the absence of 12 V on the cartridge slot.

Perhaps keyboard bounce.

Perhaps the sound or timing of the click of the cassette relay.

There is a circuit used to select the audio. I wonder if you could detect how fast that circuit can switch somehow.

If you had a RTC could you detect a timing difference between PAL and NTSC CoCos?

Could you do something with DMA? Like could you time how fast the PIA/VIA is working?

Could you hear something in the CRT / video circuit?

Could you use a telephone pickup coil to hear something in the CRT / video circuit?

Could you make a pores man's Time Domain Reflectometer (TDR) to measure trace length?

Could you hold a light pen up to the display and make a measurement? 

Could you do some kind of wraparound test? Like output something and then feed it back into the CoCo?

Isn't there a workaround in the CoCo 2 to make artifacting color graphics work?

What if you could repeat something 1000 times and notice a timing difference in the video refresh.

TIMER=0
T1=TIMER
FOR X = 1 to 1000
NEXT X
T2=TIMER
IF T1 > T2 THEN T2=T2+65536
T3=T2-T1

What if you hold an AM radio up to it and have it play a song?

What if you could measure how noisy the power supply is under certain conditions?

Is the power switch the same on the CoCo1 and CoCo2?

If the parts are socketed, then a TDR should be able to pick them up.

The thermals may be different. Cooling heatsinks and such. As current runs through an OP-AMP the offset voltage will drift until the temperature stabilizes.

-John Mark Mobley