Difference between revisions of "PDP-8"

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(for the 2 MHz clock, see "Computer Structures: Readings and Examples", page 120: "A PDP-S/S is one-fifteenth of a PDP-8 at one-half the cost. ...even though the same 2-megahertz logic clock is used in both cases.")
(fpund good sources (primarily maintenance manual) that clarifies this)
Line 14: Line 14:
| virtual address = 4k words
| virtual address = 4k words
| design type = [[clock]]ed random [[logic]]  
| design type = [[clock]]ed random [[logic]]  
| clock speed = 2 MHz
| clock speed = 1.33 MHz
| additions per second = 333
| memory speed = 1.5 μseconds
| memory speed = 1.5 μseconds
| memory mgmt = bank select
| memory mgmt = bank select

Revision as of 22:24, 19 August 2019

This article is about the first PDP-8, which had that name without a model suffix. For information about PDP-8's in general, see PDP-8 family.

An original, transistorized PDP-8
Manufacturer: DEC
Architecture: PDP-8
Year Introduced: 1965
Year Discontinued: 1969
Form Factor: minicomputer
Word Size: 12 bits
Logic Type: DTL
Design Type: clocked random logic
Clock Speed: 1.33 MHz
Memory Speed: 1.5 μseconds
Physical Address Size: 32k words (requires optional Type 183)
Virtual Address Size: 4k words
Memory Management: bank select
Bus Architecture: Negative I/O Bus
Predecessor(s): PDP-5
Successor(s): PDP-8/I
Price: US$18,500

The PDP-8 (now often known as a Straight 8; the name dates from the late 60's, apparently adopted to allow disambiguation), the first model of the PDP-8 family, was DEC's major breakthrough, and now considered the first really successful minicomputer. It was, by a significant amount, the cheapest computer yet made at the time.

The PDP-8 was constructed with discrete transistors, packaged into DEC's FLIP CHIP technology. It could perform an addition to the accumulator in 3.0 μseconds, and a 12 by 12 bit multiplication with 24 bit result in 15 μseconds (average; range 9 to 21), using the optional math extension hardware (below).


Options included:

  • Type 183 Memory Extension Control, which was needed to support more than 4k words of memory
  • Type 184 Memory Module
  • Type 188 Memory Parity
  • Type 182 Extended Arithmetic Element, which supported hardware integer multiplication and division, multi-bit double-word shifts, and normalization

Operating Systems

The PDP-8 could run various operating systems including:


There are various emulators for PDP-8 systems including:

Application software/Simulation software

Mention in this video regarding a PDP-8 screen running J.H. Conways game of life: