M-1113 PDP1spec Jun61

This document, a Permanent Memorandum dated June 27, 1961, from John Koudela, outlines the specifications for the Programmed Data Processor (PDP-1).

Central Processor:

• Architecture: 18-bit fixed word length (including sign), single-address instruction format, one instruction per word, and supports multiple-step indirect addressing. It uses fixed-point arithmetic.
• Performance: Addition and subtraction take 10 microseconds. Multiplication is 25 microseconds (automatic) or 325 microseconds (subroutine), and division is 40 microseconds (automatic) or 440 microseconds (subroutine). Most other instructions execute in 5 or 10 microseconds.
• Operation: Internal operations are parallel, synchronous, and sequential. Input-output (I/O) is generally synchronous but can achieve asynchronous/concurrent operations via programming or high-speed channels.
• Instruction Set: A total of 102 available instructions, including basic, micro-instructions, and various I/O transfer (IOT) instructions.

Storage Unit:

• Type: Random access, non-volatile, coincident-current magnetic core memory.
• Capacity: Configurable from 4,096 to 32,768 words, in 4,096-word modules.
• Word Size: Each word is 18 binary bits, equivalent to 5+ decimal digits or 3 alphanumeric characters.
• Access Time: 5 microseconds.

Input-Output Devices:

• Magnetic Tape: Up to 24 units, 200 characters/inch, 7 bits/character, 75 inches/second tape speed, 15,000 characters/second transfer rate. Includes basic (sequential) and high-speed (block transfer, concurrent operations, scatter-gather, read-compare, sorting) control units.
• Punched Tape: Photoelectric reader (400 lines/second) and punch (63 lines/second), supporting 5, 6, 7, or 8 channels (8 standard).
• Typewriter: 10 characters/second output, alphanumeric plus special characters.
• Line Printer: 450 lines/minute, 72 columns, alphanumeric plus special characters.
• Punched Card I/O: Control for IBM 523 Summary Punch, 100 cards/minute input/output.

Special Equipment:

• Sequence Break System: Allows concurrent operation of multiple I/O devices (1-channel standard, 16-channel optional).
• Cathode Ray Tube (CRT) Display & Light Pen: Displays at 20,000 points/second, with 16" (1:1024 resolution) and 5" (1:4096 resolution) options.
• Real Time Clock: An 18-bit binary counter.
• High-speed I/O channels, I/O instruction control panel, and a basic spare parts package.

Checking Features: Includes accumulator overflow, lateral parity checks on magnetic tape, magnetic tape read-compare, and built-in marginal checking facilities.

Physical & Environmental:

• Dimensions: 98.5" W x 24.5" D x 69.5" H.
• Weight: 1500 pounds.
• Power: 115 volts, 60 cycles/second, single phase, 1500 watts.
• Environment: Operates between 50-110°F and 20-70% relative humidity. No special site preparation required.

Production & Services (as of June 1961):

• Delivery: 6-9 months from order.
• Systems Produced: Over 5.
• Support: Includes a basic program/subroutine library (FRAP, DECAL, floating/fixed point packages, utility routines), programming/operating/maintenance training, and access to an active PDP-1 User's Society.

A Standard PDP-1 Computer System includes the Central Processor (with 4,096 words of 18-bit core memory), Control Console, Punched Tape Reader, Punched Tape Punch, Alphanumeric Typewriter, One Channel Sequence Break System, Input-Output Instruction Control Panel, and programmed multiply/divide using step instructions.