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A project log for Ferrite Core Memory Module

A sub-project of the ED-64 Computer to document the development of a 64-byte ferrite core memory module

Andrew StarrAndrew Starr 04/10/2017 at 08:0212 Comments

Reading, writing, and repairing.

The last few weeks have seen significant progress, to the point where I can read and write data to the the cores, with the following limitations:

1. I screwed up the design of the Inhibit module, so I can only write 1 zero in a byte. I have corrected the module design, and I expect the corrected boards to arrive any day now.

2. The system currently takes about 30 mins to warm up. If I run a continuous memory test on the cores (writing 0xFFs/0xEFs), a serial printout of erroneous memory locations gradually gets shorter and shorter, until they're all ok. I'm not sure what the issue is, but I suspect the bias diodes (1N4148s) in the sense amplifiers. The sense amplifiers are a bit kludgey, so I'm reluctant to disturb them too much until I have corrected boards for them - the next job, after the inhibit module. Then I can investigate properly, without worrying about breaking shitty soldering joints or shorting kludge wires.

Anyway, here's a few pics of the current setup:

In the picture above you can see my Quality Assurance Technician (QAT) hard at work.

The rear of the memory system, currently controlled with a Arduino Mega 2560, and the power supply. Note the cat-5e cables - this is how the various computer subsystems will be interconnected.

Discussions

Stuart Longland wrote 04/13/2017 at 10:29 point

The quality assurance technician doesn't look too happy about the state of things… ;-)

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Yann Guidon / YGDES wrote 04/13/2017 at 12:30 point

The quality assurance technician's work is not to be happy...

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Andrew Starr wrote 04/13/2017 at 22:39 point

Of course not, she isn't being fed at that particular moment :)

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Yann Guidon / YGDES wrote 04/13/2017 at 23:52 point

obviously not :-)

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Stuart Longland wrote 04/14/2017 at 00:33 point

Ahh, and of course unhappy that you are being a disobedient human… don't you know, feline needs come first?

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Blecky wrote 04/19/2017 at 11:02 point

"The F is this shit? I'm writing you up!"

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Yann Guidon / YGDES wrote 04/10/2017 at 08:09 point

Where do you get these fine boards manufactured ?

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Andrew Starr wrote 04/10/2017 at 08:12 point

pcbway.com. They're the one of the cheapest board houses out there, and the quality is good.

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Yann Guidon / YGDES wrote 04/10/2017 at 08:23 point

your base boards are quite large, how much did they cost ?

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Andrew Starr wrote 04/10/2017 at 08:28 point

The base boards are 275 x 177mm, 4 layers. Currently US$216 for 5, including freight to La Belle France :)

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Yann Guidon / YGDES wrote 04/10/2017 at 08:05 point

Meow...

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Andrew Starr wrote 04/10/2017 at 08:08 point

Damn thing is a camera hog

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