[Coco] Aussie 2 meg installation - results

[Bob Devries]

Robert Gault said:
> What does "pulling the plug from the memory board" mean? Does that 
> disconnect the four wires going to the DAT or something else? If the 
> memory board is disconnected, does that mean there is still 512K 
> conventional memory installed in the Coco3

Yes, pulling the plug means disconnecting the DAT board from the MEM board.
There is no on-board memory in the coco3, it had been used previously as a 
512K coco3.
So also, all the capacitors were already cut (i double-checked)

>  If the simms are faulty, swapping them might show something of interest. 
> What happens if you try running with just one simm?

The computer won't run on just one SIMM.
I replaced both SIMMS, and there was no difference.

>  Your choice of 150 ohms for the resistor is based on the NTSC schematics 
> but you don't have an equivalent circuit. It seems you need a high 
> impedance input to the memory board to prevent degradation of the master 
> clock signal. However, without a scope on GIME pin#2 you can't tell 
> whether 150 ohms a large enough value. Still as the Coco boots, 150 ohms 
> probably is OK.

True, the choice of 150 ohms was based on the NTSC design, but I had to 
start *somewhere*.
It seems to work. Maybe I'll try to increase the value to say 1K or 4K7.


--
Regards, Bob Devries, Dalby, Queensland, Australia

Isaiah 50:4 The sovereign Lord has given me
the capacity to be his spokesman,
so that I know how to help the weary.

website: http://www.home.gil.com.au/~bdevasl
my blog: http://bdevries.invigorated.org/