[Coco] 2 MB upgrade in PAL coco3

[Bob Devries]

Hi Mark,

My first thought would be to insert a 74F04 in the clock line from the 
crystal oven, to ensure that there is sufficient signal for the upgrade. 
Sadly, I don't have an oscilloscope which will read this signal :(

--
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/

----- Original Message ----- 
From: "Mark Marlette" <mark at cloud9tech.com>
To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
Sent: Monday, January 21, 2008 10:42 AM
Subject: Re: [Coco] 2 MB upgrade in PAL coco3


> 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
>>
>>
>>
>>
>>--
>>No virus found in this incoming message.
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>


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