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Manufacturer DEC - Digital Equipment Corporation Identification,ID PDP-5 Date of first manufacture 1963? Number produced - Estimated price or cost - location in museum - donor -
Contents of this page:
- Special Features
- Historical Notes
- This Specimen
- Interesting Web Sites
- Other information
Word size - 12 bit words, Max addressable memory - 4096 words max The 12 bit accumulator had a 13th bit (past high order bit) was "link bit". The "link bit" was very useful in multi-precision arithmetic - common in a machine that can only count 0 to 4095. 8 instructions, instruction code was 3 bits - see "small computer handbook" This makes the modern "RISC" machines look "complex" like the CISC machines! Op Code bits 000 - 001 - 010 - Conditional Skip Instruction, TRUE skipped the next instruction. The next instruction could be a jump instruction. Remaining 9 bits defined the skip conditions such as: skip on zero, skip on negative, 011 - Deposit Accumulator (store accumulator) and sets accumulator to zeros 100 - 101 - 110 - Jump to Subroutines, return address placed at target address, and execution started one address higher 111 - Unconditional Jump Instruction format (12 bit word) ------------------------------------------------------ 3 bits opcode | 1 bit page | 1 bit indirect | 7 bits of address (see above) --------------------------------------------------------------- page bit - if 0 - then use low memory (ignore hi 5 bits of P register) if 1 - use "current page (use hi 5 bits of P register) indirect bit - if 0 - use regular addressing if 1 - use address as indirect address 7 bits of address - low seven bits of addressing ---------- start page 0 description ------------ Memory locations 000 - 177 octal 000 007 = normal page 0 memory 010 017 = special memory, refered to as autoincrementing locations If you referenced it indirectly, it autoincremented you can do a block move using 2 autoindex locations. This concept copied by Ed DeCastro for the Data General NOVA series. 020 177 = normal page 0 memory ---------- end of page 0 description ---------- DEC divided memory into 128, 177 octal pages There was no load instruction, you deposited the accumulator, which cleared it, then added the operand to the zero. The disadvantages of this system were - the inability to address more than 4096 words, - the addressing across the 128 pages was really awkward, - the 128 page zero words required careful management. The advantages of this system were - you could do a surprising amount in 4096 12 bit words - including compile and run a FORTRAN program - price, price, price.
see Architecture and Timeline at PDP-8.
from PDP-8 Summary of Models and Options
- P register (Instruction counter) was in memory
- Macro 5 was assembler,
- Subject: What is a PDP-5? Date of introduction: Aug 11, 1963, unveiled at WESCON. Date of withdrawal: early 1967. Total production run: 116. Price: $27,000 Technology: The PDP-5 was built with DEC System Modules, the original line of transistorized logic modules sold by DEC. The supply voltages were +10 and -15 volts, with logic levels of -3 (logic 1) and 0 (logic 0). Logic was packaged on boards that were about 4.75 inches high with each card mounted in a metal frame with a 22 pin edge connector. Input output devices were connected to the daisy-chained I/O bus using military-style armored cables and connectors. Use of toggle switches (as opposed to slide switches) on the front panel was another vestige of military-style design. Reason for introduction: This machine was inspired by the success of the CDC-160, Seymour Cray's 12 bit minicomputer, and by the success of the LINC, a machine that was built by DEC customers out of System modules. These demonstrated that there was a market for a small inexpensive computer, and from the start, DEC's advertisements were aimed at this market. "Now you can own the PDP-5 computer for what a core memory alone used to cost: $27,000", ran one 1964 ad. Ken Olson has stated that the PDP-5 was not originally meant to be a computer; it was designed for a company that wanted an automatic controller for some industrial work. He told them they could make a small programmable controller instead of the hardwired machine they were asking for, and since they weren't entirely certain of the control equations they wanted to run, they accepted the idea. The result was the PDP-5.
DEC produced a lot of inexpensive manuals. They were passed out free at trade shows, intended for the college crowd. Many high school kids snuck into those shows, and learned computers from those books.
From "Digital at Work" , Digital Press, copyright 1992, page 49
12-Bit Family Timeline 1962 Laboratory Instrument Computer (LINC) developed at MIT 1963 PDP-5, Digital's first 12-bit computer 1965 "Classic" PDP-8 world's first mass-produced minicomputer 1966 LINC-8 combines LINC and PDP-8 processors PDP- 8/S, serial version of the PDP-8 1967 PDP-8 systems manufactured in Reading, England Annual sales:$38 million 1968 LAB-8, small, general-purpose laboratory package TSS/8 timesharing software PDP-8/I, integrated circuit version of be PD18 PDP-8/L 1969 PDP-12, third member of LINC family 1970 PDP-8/E features OMNIBUS synchronous bus for bidirectional communications between system elements TABS-8 newspaper application 1971 PDP-8/M, OEM version of 8/E 1972 PDP-8/F 1974 PDP-8/A miniprocessor PDP-8/A package allows OEMs choice of memory type and quantity 1976 PDP-8/A 600 series WPS-8 word-processing software CMOS-8 chip 1977 VT78,complete PDP-8 system in a terminal, uses the CMOS-8 chip, anticipating the DECmate series WS 102, multiuser WPS 1982 DECmateII word processor 1984 DECmate III
Interesting Web Sites
- Digital Equipment Corporation PDP-5 Manual, 1964 @7.2MB.
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Updated February 6, 2002