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

Here is a review of recent known PDP-8 sales. As ever, prices appear to be heading upwards.

PDP-8/M

Ebay US sale, item #260385453584. Sold for £1023.23 / $1500.00

Original Description:

Winning Bidder will receive one (1) Complete 100% Working Digital pdp8M Computer with 8k of Iron core memory, the computer comes with the below listed boards, unit was removed from a 100% operational cnc control cabinet. Listed shipping fee for lower 48 only. (The top cover is included)

M8330 Timing Generator

M8300 Majo Registers

M8310 Major Registers Control

M837 Memory Extension Control

M847 ROM

M848 Power Fail / Auto Restart

G111 Sense Inhibit (1 of 3 8k stack)

H212 Planar Stack (2 of 3 8k stack)

G233 XY Driver (3 of 3 8k stack)

W968 I/O Interface

M849 Shield

M8320 Bus Load Module

Commentary

A very nice looking 8-M. The 8-M is a nice compact machine and this one looks like it should make its new owner very happy. The price seemed to be about spot on for a working 8-M. Interestingly its RF shield appears to be in the wrong location, I would normally expect it to sit between the CPU/options and core memory.

PDP-8/A

Ebay US sale, item #230334635912. Sold for £525.25 / $769.99

Original Description

Dec PDP-8/a computer removed from a working machine ( Wire EDM ) seems clean and in good condition but due to it’s age I cannot guarantee its operation.
Includes boards M8315 M8317 M8316 H219B G649 Power supply and an AXIS Board.

Computer has been in storage for 10+ years – it IS dusty, and needs cleaning – Collectors please note! the computer did run when removed but there is no guarantee to it’s current operation, sold AS IS because of it’s age .

Commentary

A very clean looking machine. Price was in my opinion on the high side given that the machine is the less desirable 8/A and not in known working condition. The machine has (for an 8/A) a fairly modest 8KW of core memory.

Pricing machines like PDP-8s is a difficult task. Due to the small numbers that change hands in any given year, it is often hard to put a firm price on them. It is however important for us to put a value on our collect not least to ensure that we are adequately insured against any disaster that might befall our beloved machines.

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