Actually, thats probably a reasonable price. Core memory boards, probably non-working, have been going for a high price. Age and a nice visible setup increase the price. Now, I havent seen the memory in question. but the pdp8/e core memory i've seen is all covered by a clear plastic shield. This increases its value as a display piece, as you can easily see all the core, and its all protected. Of course, in order to use the core on a pdp8/? you would need a couple of support boards in addition to the core plane board itself. I would say that just the core plane, being of a nice size, and being very good 'visually' to display, and somewhat because its a PDP8 series board (nostalgia value), that its probably worth $100 all by itself. If it comes with the 2 support boards and the top connector things at that price, then i'd say its a bargain. Just my 2cents. -Lawrence LeMay

At 04:58 AM 4/19/99 -0700, Ethan Dicks wrote: As Allison pointed out, its called a "stack" for a reason as I've discovered over the last 20 months. Core memory consists of three major elements, the select logic, the planes themselves, and a set of current source/sense amplifiers that are used to drive it. Depending on the design these can be somewhat generic or not at all generic. The absolute best value is to get a complete set of core plane boards that came out of the DEC factory working. The second best is to get a set that DEC had refurbished, and everything else loses value from there. When I joined this list, I did so because I was looking for some memory for a PDP-8/M that I had. The system was complete except for memory. Later, I discovered that 4K wasn't sufficient really to run much more than the paper tape stuff so I really needed 8K. I have searched fairly widely, both through the internet and through the "unofficial" DEC channels. This is what I've discovered. DEC spares still carries core for the 8/e/f/m, 4k is $1,725 per set. Ideally you need 12K for OS/8 and that means you really want an 8/E dual backplane or an expansion box. Many of the DEC "wholesalers" have a very small selection of OMNIBUS boards, I discovered Mitch over at Keyways and bought from him a G104, G227, and H220 board (one 4K stack), but they were not a matched set. (total cost $275) While Mitch would have been happy to take them back, I chose to keep them on the assumption that getting a complete set working would be easier than finding a complete set. Every now and then one of the wholesalers has a complete PDP-8 for sale. I found one in LA for $800. I had a friend check it out and it was a dead 8/f. Memory was third party (DATARAM) and couldn't be verified. Pass. Two months ago I found an 8/M at auction at SRI with a 8K stack and a 4K stack in it. I bid $206 and won it. Amazingly it actually worked so I either managed to get memory for my non-working 8/M or I still have an 8/M with no memory and an extra 8/M. :-) The bottom line is that real honest to god core that works is pretty hard to come by. I've never seen any core for the 8/I or 8/L (except the ebay one, and the 8/L that wsa offered for trade on this list). There is an excellent theory of operation on core planes in the PDP-8/a miniprocessor users handbook. Between that, my current probe, and my scope I believe I can get the dead 4K stack I've got running again. And I'm currently building a 32KW semiconductor board so that I'll have a backup. --Chuck