List of Programmed Data Processors

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Programmed Data Processor was the name adopted by Digital Equipment Corporation for all its early computers. (Reportedly, it was adopted to avoid worrying its early venture capital backers; at the time, almost all computers were large mainframes, and DEC's founders were concerned that if it appeared that they intended to compete in that market, they wouldn't be able to get funding.)

The name was dropped starting with the VAX. The other PDP families which became actual products for DEC (most included more than one model) were:

Family/Machine Word Size Comment
PDP-1 18
PDP-3 36 Only one built, not by DEC
PDP-4 18
PDP-5 12 First minicomputer
PDP-6 36
PDP-7 18 Original UNIX machine
PDP-8 12 First commercially successful minicomputer
PDP-9 18
PDP-10 36 DEC's mainframe. Renamed DECsystem-10, and later added DECSYSTEM-20.
PDP-11 16
PDP-12 12 Laboratory computer, replacement for the LINC-8
PDP-14 12 Industrial controller
PDP-15 18
PDP-16   Not an actual computer; custom industrial controllers built out of Register Transfer Modules

A number of other PDPs never existed as real machines, are misnomers, or jokes:

Family/Machine Word Size Comment
PDP-2 24 Never designed.
PDP-2½  ? Jocular moniker for "CASINO" by Ed Rawson of the American Science Institute.
PDP-13 The unlucky number 13 was skipped.
PDP-20 36 Not a real name! Sometimes used for DEC-20 computers.
PDP-24 24? Unconfirmed, mentioned in PDP-X memo 3.
PDP-K 18 Intended as a bridge between the PDP-15 and the PDP-10 family, with a PDP-11-like instruction set.
PDP-X 16 An alternative to the PDP-11.

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