Consolidated Computer Inc. PDP-8 Clone – Part 7. the memory boards.

Having taken a look at and a brush to, the first few boards, I have come to the memory boards. This machine has 32kwords of 13 bit core memory in two memory modules.

There is a memory bus controller board but I didn’t take a photo of that. I did get photos of the memory modules themselves though.

Top view of the 16kw x 13 bit core memory module.

The memory modules were made by Ampex and have a customer part number containing the initials CCI. This must mean the boards were made specifically for CCI and were not off-the-shelf-items just bought in.

Looking from either side of the module it is not overly obvious that there is any core memory at all. It’s well protected between the two PCBs that make up the module.

Identical in every way?

When I was cleaning the first of the modules I noticed a broken resistor. I struggled to read the value bands so I took a look at the other module, one I hadn’t cleaned at all, and it had the same broken resistor!

Two view of the upper memory board showing the broken resistor

I had a word on the VCFED forums and the view of the team was that the resistors were 510 Ohms. A quick raid of the parts bags and two new resistors were fitted.

Top view of the upper memory board showing the replacement resistor.

Having to part the two boards that make up each memory module gave me the opportunity to take a look at the core memory itself.

The core array is behind a steel plate and a sticker warning me that I was about the void the warranty.

View of the core memory array.

I was very careful when removing the metal plate and I’m glad that I was. This is the smallest core I have see I think. Sadly I don’t have a standard banana for scale but trust me, the cores are tiny.

Close up of the core memory array.

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