[Coco] CoCo 3 RAM upgrade question
mmarlette at frontiernet.net
Wed Feb 1 18:37:19 EST 2012
These are the RAS / CAS filter caps.
I would one lead of both caps Try to leave a bit of the lead intact in case you want to return it to 128K configuration.
What is mostly likely occurring is that with all of the chips, x4, the added capacitance is skewing / loading the RAS/CAS signal down.
Doing this will not effect any 512k board I have ever seen.
After the clip, it still might not work, in that case, the RAM is bad. Always fun to find the bad ONE!!!
You are getting an education. from the floppy controller to DRAM! :)
----- Original Message -----
From: "Boisy G. Pitre" <boisy at tee-boy.com>
To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
Sent: Wednesday, February 1, 2012 2:46:21 PM
Subject: Re: [Coco] CoCo 3 RAM upgrade question
The upgrade board you have is not the Cloud-9 512K SIMM board (I'm not sure what kind it is, actually), so i am hesitant to say clip C66. I'll let Mark chime in, but I think you're safe in leaving C66 in place.
Boisy G. Pitre
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On Feb 1, 2012, at 2:22 PM, Blake Patterson wrote:
> So, part of the haul of CoCo items I got in this recent package was a somewhat hacked up CoCo 3 bare motherboard with a 512K RAM expansion on it. I removed it and performed the upgrade to my main CoCo 3.
> To figure out the drill I looked over at Cloud9 for instructions on their SIMM board. It said to pull the 4 existing RAM chips and clip the upper C64 cap and the lower C65 cap. I noticed on the CoCo 3 that this upgrade came from that the C65 (lower) cap was clipped, but not the C66 (upper) cap. This is contrary to the Cloud9 instructions, but perhaps it's a different drill for different boards?
> The system powers up fine with the upgrade in it, but still I get just a few blocks read through DriveWire before it just sits there on almost every OS9 boot I perform using "DOS" command. Boisy thought maybe I was running out of RAM -- was hoping that things would be working now.
> Do I need to clip that upper cap? Is the RAM not fully recognized?
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