A few PDP-8s have come up recently on Ebay. Here is a summary of the highlights:

PDP-8/L

This PDP had lived its last 30 years on a barn, although the pictures don’t look too bad. Internally very clean and looks like it has a complete set of cards including memory. The outside is not so pretty much probably mostly surface rust and dirt although it does have one missing toggle key.

Sold for $1026.99 / £710 which seems a fair price for such an early machine

PDP-8/M

Described as being ‘museum quality’, this very clean PDP-8/M came nicely loaded with 16KW of memory (non DEC Plessey core cards), programmers console,  a serial interface and the extended memory/timeshare module (required for >4KW of memory). The machine was in full working order.

Sold for $3050 / £2110. This I feel is a very high price with the buyer prepared to pay a premium for such a clean and working machine.

PDP-8/M

From the same seller as the 8-L above, this 8/M is in cosmetically fair condition looking clean on the inside but suffering from some surface rust on the outside. The machine comes with the basic front panel (which is fairly unusual), extended memory/timeshare option and 8KW of memory. Interestingly it lacks any form of bootstrap which it would really need in order to get it to do anything useful.

Sale price $677 / £468 which I feel is about spot on for what is a very restorable machine.

PDP-8/A

Recently removed from real world service in CNC machines, a very clean and well specified PDP-8/A coming with programmers console, 16KW of core, option and extended option boards. Seller also had seperately a paper tape reader (non DEC) and controller.

Sale price £341.78 which is about correct for the less desirable -A’s

This table details locations of cards on a PDP-8/L backplane. I’ve put it together to aid in working out what is missing from my 8/L. I believe it to be accurate but you are encouraged to double check!

Optional data break interface
Optional memory parity
Optional power fail
Optional high speed reader and/or punch

A couple of new machines have joined my stable, a very clean PDP-8/L and another PDP-8/E.

The /L is complete with the (somewhat important) exception of its core stack which has been lost at some point. If anyone has or knows the whereabouts of a spare stack (I believe they were common to the /I and PDP-12), please let me know. If I can’t find one I will have to resort to fabricating an alternative using NVRAM chips,although I doubt this will be trivial.

The /E is generally clean although its plexy is pretty scrappy. I quite like the dog eared look and so I will leave it this way. The console itself is missing a couple of keys although I have replacements for these. The machine came with no cards, but I have spare CPU sets and so I’m only left needing to find memory which should be achievable.