PDP-8/E

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PDP-8/E
PDP 8 e Trondheim.jpg
PDP-8/E front panel
Year Introduced: 1970
Form Factor: minicomputer
Word Size: 12
Logic Type: TTL
Design Type: clocked random logic
Clock Speed: 385KHz
Memory Speed: 1.2 μseconds
Physical Address Size: 32KW (requires optional KM8-E)
Virtual Address Size: 4KW
Memory Management: bank selection, CPU mode
Bus Architecture: OMNIBUS
Operating System: OS/8, TSS/8
Predecessor(s): PDP-8/I
Successor(s): PDP-8/A


The PDP-8/E was an improved model in the PDP-8 line, and introduced the OMNIBUS for interfacing to device controllers.

The PDP-8/F was a cost-reduced version of the -8/E with the same CPU and main memory, but only a single OMNIBUS backplane. The PDP-8/M is the OEM version of the PDP-8/F.

The -8/E's KK8-E CPU consists of five quad boards; the MM8-E core memory that was standard on the -8/E consisted of sets of three quad boards.

Options included:

  • KA8-E Positive I/O Bus Interface, to allow use of older PDP-8 devices
  • KM8-E Memory Extension and Time-Share Option, which was needed to support more than 4K words of memory, and allowed the computer to operate in either Executive Mode or User Mode
  • MP8-E Memory Parity
  • KE8-E Extended Arithmetic Element, which supported hardware integer multiplication and division, one-bit double-word shifts, and normalization

It could perform an addition to the accumulator in 2.6 μseconds, and a 12 by 12 bit multiplication with 24 bit result in 40 μseconds, using the math extension hardware.

The -8/M could be supplied with either a KC8-M Operator's Console, or a KC8-ML Programmer's Console, the latter being basically identical to the KC8-EA Programmer's Console of the basic -8/E.