Here is a response about reviving old core memory boards, from Kevin 'kevtris' Horton, who has revived 3 of them in the past. -------- Forwarded Message -------- Subject: Re: Fwd: [vcf-midatlantic] Core Memory Purchase Date: Thu, 3 Dec 2015 01:15:52 -0500 From: K Horton <kevtris@comcast.net> To: Jonathan Gevaryahu <jgevaryahu@gmail.com> On 12/2/2015 22:17 , Jonathan Gevaryahu wrote:

kevtris, you have some experience resurrecting core memory. Do you want to respond here?

-------- Forwarded Message -------- Subject: [vcf-midatlantic] Core Memory Purchase Date: Wed, 2 Dec 2015 16:56:35 -0800 From: John Sully via vcf-midatlantic <vcf-midatlantic@lists.vintagecomputerfederation.org> Reply-To: vcf-midatlantic <vcf-midatlantic@lists.vintagecomputerfederation.org> To: vcf-midatlantic@lists.vintagecomputerfederation.org CC: John Sully <john@csquare.ca>

I'm planning to resurrect some old core memory as a hobby project. I was wondering if anyone with experience on getting this memory working could provide some insights on what I should look for.

EBay seems to have a large number of expensive ones that don't appear to be in working order - along with some much cheaper (relatively speaking) russian made stacks.

yes, this is a big problem. if the core memory is shown "open" on ebay, don't buy it. there's a 99% chance it's going to be broken. The cores and wiring are extremely fragile, just blowing on it can destroy it (well not THAT bad, but it's still pretty insanely fragile). I have three fully working core memory boards: two 16K*18 and one 32K*18 boards. I had to fix all three of them, since they had bad parts here and there, but it wasn't TOO hard. All of them work similar; there's a hardware state machine that runs a little sequence for reads that do this: read the word, then write the same data back (since reading core is destructive). I successfully dumped the data that was sitting on all three of my core boards; the 16K boards were repaired and put in stock as spares apparently, and just had a 0101010101 pattern, while the 32K board contained actual NASA code! I dumped it but lost 256 words of data, unfortunately. That board had some problems with reading/writing because there was a bad transistor in the X driver, and there was a bad TTL chip. All of them had bad tantalum caps that I had to replace; the 32K board kept randomly drawing enough power to trip the current limit on my power supply every few hours, so I finally found it and replaced the cap which fixed that. The 32K board is extremely "advanced', compared to the 16K boards which are more traditional. The 32K board only has a single X and single Y driver instead of a bunch of each. All of them have a forest of transistor arrays, diodes, and pulse transformers to do selection because it saves a ton of hardware this way. I have a dir on my website with all the stuff I did on it and if there's interest I can make a video showing off my rig and how I tested the memory. I had schematics I drew for the boards but I think I might've lost them. there's some PDFs in there that give esoteric details on the care and feeding of core memory. http://blog.kevtris.org/blogfiles/corememory/