[Coco] 2 MB upgrade in PAL coco3

[Mark Marlette]

Bob,

Doesn't surprise me. Tony used an analog timing circuit with 
components that we +/- 20%.

I have one that I have never been able to get to work either. Mostly 
because I look at the design and it is a waste of my time to tweak 
the circuit. I would rather redesign and make the circuit digitally 
timed and solid. Tweaking will always lead to tweaking. Worked for 
Tony in the day when he supported it. Today there are MUCH better 
ways to implement the timing required to put larger DRAMs in the CoCo.

Grab a scope and chase those trons.....Tweak away......When you are 
done you will be an expert in the CoCo's refresh. :)

Regards,

Mark





At 1/20/2008 06:29 PM, you wrote:

>Hello, fellow coconuts.
>
>I brought this topic up some time ago, with no resolution, so I'll 
>present it again.
>
>I have a Disto 2MB upgrade board here that I have tried to install 
>into my Australian PAL coco3. Physical installation was fine, but... 
>it just doesn't work.
>
>I believe there was at one time a discussion regarding this problem 
>on either Delphi or Compuserve. If anyone has the complete 
>transcript of this, or has knowledge of the problem, I'd appreciate 
>getting the information.
>
>My guess is that it is a timing problem, or the clock signal used 
>isn't correct somehow. The only change from the installation 
>instructions is the connection of the clock signal. On the 
>Australian Coco3, the master clock is supplied by a crystal oven; 
>one of those small rectangular metal minidip devices with 4 pins. 
>This signal connects to pins 2 (signal) and 3 (ground) of the GIME. 
>I connected the upgrade clock signal to pin 2 of the GIME. The 
>crystal oven's frequency is 28.475 MHz.
>
>Can anyone help with this?
>
>--
>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/
>
>
>--
>Coco mailing list
>Coco at maltedmedia.com
>http://five.pairlist.net/mailman/listinfo/coco
>
>
>
>
>--
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