Microtape

This document provides a technical overview and specifications for the Digital Equipment Corporation Microtape system, consisting of the Type 555 Dual Tape Transport and the Type 550 Tape Control.

Key Features and Capabilities:

• System Design: The system utilizes a simple, reliable mechanical transport with no capstans or pressure pads. It supports bi-directional operation and uses redundant, phase-recorded tracks to minimize data errors and skew.
• Addressing and Format: Microtape features fixed position addressing, allowing for the selective updating of specific words or blocks without disturbing surrounding data. Pre-recorded timing and mark tracks allow for automatic block/word addressability.
• Performance: The 555 transport uses 3/4-inch Mylar tape with a capacity of approximately 3 million bits per 3 1/2-inch reel and offers an effective transfer rate of 90,000 bits per second.
• Integration: The Type 550 Control can manage up to four 555 transports (8 drives) for use with PDP-1 and PDP-4 computers. It supports various programmed modes, including Search, Read, Write, and Move.
• Software Support: The system includes pre-tested subroutines for information storage and retrieval, as well as diagnostic and maintenance routines (MICROTOG) and an information management tool (MICROTRIEVE) accessible via console switches.

The document concludes with a detailed instruction set for both the PDP-1 and PDP-4, operational flag charts, and comprehensive physical and performance specifications for the hardware.