[Coco] Aussie 2 meg installation - results

[Bob Devries]

Well, I installed the 2 Meg board as per instructions (Well, almost).

Firstly, I just connected it as I would expect it to work, that is the DAT 
board is in, the memory board is in with 2 1MB SIMMS. 4 wires go from the 
DAT to the mem board, and one from the mem board to GIME pin 2, and one from 
the mem board to Pin 40 of IC5.

This did not give a workable screen, however, when the plug on the mem board 
was removed, BASIC came up as usual.

I then inserted a 150 ohm resistor in series with the wire from pin 2 of the 
GIME (the resistor as close as I can get to the GIME), and fired up again.
Hey presto, it comes up right now.

Run the supplied MEMTEST program.

This goes through until it gets to block 47 ($2F), and quits - BAD MEMORY.
If I now pull the plug off the mem board, and run the test again, it does 
the same; i.e. gets to block 47 and quits.

A couple of things come to mind:
- The Coco3 I am using may be flaky.
- The 2 Meg kit may be faulty. I have no way of testing this.
- the wires between the DAT and MEM board are too long and/or need some 
shielding. (the wire from GIME pin 2 needed to be run from the bottom of the 
motherboard. Maybe I should run that in shielded cable?
- The SIMMS may be faulty.

Any comments from the hardware gurus?

--
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/