PDP-5

The PDP-5 was DEC's first 12-bit computer, the predecessor to the PDP-8. Like the -8, it was a load-store architecture. A memory extension unit was added later, to support bank switching, and thus allow the use of more than 4KW of main memory.

It was built out of the standard modules created for the PDP-4. It was built using the bit-slice concept, where one bit of all the registers and the data paths between them was implemented on a single PCB; a number of these boards (equal to the word length of the machine) formed the CPU. To minimize the initial cost, it had an I/O bus, rather than the radial links from the CPU to individual peripherals used in all earlier DEC machines, such as the 18-bit machines like the PDP-1.

External links

• PDP-5 - ducumentation at Bitsavers
• PDP-5 Manual
• C. Gordon Bell and John E. McNamara, The PDP-8 and Other 12-Bit Computers, in C. Gordon Bell, J. Craig Mudge, John. E. McNamara, Computer Engineering: A DEC View of Hardware Systems Design, Digital Press, Bedford, 1978