ICT 1301 - Hardware

ICT 1301 - technical specifications

The 1300 series was a second generation range of computers. They were built with discrete Germanium PNP transistors and diodes. The design positioned them as cost efficient work horses for commerce, eg payroll & accounting, not one or two off machines built for maximum performance at any cost for military or scientific work. The 'basic' 1301 has three peripherals, a card reader for 80 column punched cards operating at 600 cards per minute, a line printer with 120 columns operating at 600 lines per minute and a card punch operating at 100 cards per minute. The CPU has intimate control of the peripherals, this unbuffered approach saves a lot of circuitry and hence cost. The performance of the peripherals was quite high for the period. The basic machine has core storage and a drum backing store. Additional to this was the optional magnetic tape sub system, which is buffered and contains almost as many logic circuits as the basic machine. It roughly doubled the cost of the machine when new, which in total cost around a quarter of a million pounds. This sub system consists of the Data Transfer Unit (DTU) and interfaces for magnetic tape drives (up to eight could be supported).

ICT 1301 system layout
The system lay out scanned from an original brochure. Note: On this early image, J is actually the Data Transfer Unit (DTU) and the tape system control which ran perpendicular to the end of J is missing! ict1301.co.uk

ICT 1301 computer = with 1 inch Magnetic Tape. Just a few approximate vital statistics of the machine, follows:-

Width = 20ft , Length = 22ft , Power = 3 Phase industrial Supply

Approx. 7352 Germanium transistors, (and one single valve) used to produce a lot of heat, and if the temperature got too high, the resultant problems caused, would take a lot of hard work to locate. Printed circuit boards were not pluggable, so when you thought you had found the duff board all you had to do was, power off, remove up to 25 wire wrap connections, replace the board, remake up to 25 wire wrap connections. Then you crossed your fingers and powered up again.

Speed = 1MHz Clock, Processing was 4 bits wide, serial 12 digits, 3 primary data registers, plus 3 control registers. All the arithmetic functions were in decimal format, with an alternate set of functions for processing Pounds, shillings and pence.

Program storage was 2 thousand 12 digit words of fast, 'Immediate Access Store'. This was ferrite core store and with twelve digit words this equates to 12 kilo bytes.

Further Program Store was on Drum with twelve thousand words of Drum storage, again the 12 digit words make it Seventy two Kilo bytes of Drum, which could provide overlay techniques for program area's.

This machine shown also has 4 one inch magnetic tape units each with a storage capability of 1.5 million twelve digit words approx, around Nine Mega bytes of storage.

Input Output was on punched 80 column cards with 600 line per min printed output.

Typical work for this type of machine was to do batch processing, of large datafiles held on magnetic tape, although some alternative applications were attempted. No assembler was used by the programming staff, this was a direct machine code driven beast, or computing in the raw.

Information from The ICT 1301 Resurrection Project at http://www.ict1301.co.uk/. More will follow on this page as time permits!