IBM COMPATIBLE 9-TRACK TAPE SYSTEM FOR THE PDP-8 COMPUTER

A control unit design to operate a 9-track tape system with a PDP-8 computer is described in detail. In addition to providing a local bulk storage facility, the tape system is designed to operate on IBM Compatible 800bpi tapes and hence information interchange with System 360 installations is possible. The formatting scheme is such that data transfers between the PDP-8 and the tape unit always take place as 12 bit parallel words. This not only means full use of the available memory space in the PDP-8, but also makes programming the tape system efficient and easier. An unique by-product of the formatting scheme is that the End-of-File Code is the only record with a single character as data on the tape. This makes it unnecessary to rely on the code read from the tape to identify the End-of-File and correspondingly the End-of-File detection logic is very simple. This research was supported by the Canadian Hydrographic Service, Marine Sciences Branch