List of Programmed Data Processors
From Computer History Wiki
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 | The first PDP |
| PDP-3 | 36 | Only one built, not by DEC |
| PDP-4 | 18 | Simplified and cost-reduced 18-bit machine. |
| PDP-5 | 12 | The first minicomputer |
| PDP-6 | 36 | DEC's first "large" machine; immediate predecessor to the PDP-10 family |
| 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 | The last 18-bit PDP |
| 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 DECSYSTEM-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. |
