Tuesday, August 23, 2011

ICL System 4/50 .... RCA Spectra 70/45

In the late 1960s I  worked  on a project at the Post Office in London that used System 4s and Spectras, both clones of the IBM 360 mainframe.

The hardware had been bought for National Giro, the government's bank-for-the-ordinary-man, based in Bootle, Merseyside.  Unfortunately the bank was not as sucessful as predicted, leaving a lot of spare hardware. 

Rather than admit the Giro's lack of success, the Post Office created a number of new projects and pretended that the hardware had been bought for theses projects. So I ended up as one of the designers of a real-time operating system that was to support a system for managing long-distance phone lines.

The project included about 40 new graduates and, as I was the only one who knew anything about computers, I got to design part of the system and to work on the operating system's memory management.

After the project had been going almost a year we had some minor management changes, including a women who thought that the project seemed a lot like the project that her husband was working on in another Post Office building.  It turns out that the two projects were identical!!

The two projects were chopped in half and the back-end of one merged with the front-end of the other.

This removed the justification for the operating system, so I was re-assigned to lead a team of Cobol programmers. The programmers were sent on a Cobol course while I was given a copy of Daniel McCracken's book on Cobol..

I so enjoyed Cobol programming that I set about looking for someone who needed an operating system designed..

The Elliot 803

The Elliot 803 was the first computer that I did any serious programming with in the 1960s. It came with a massive 4k (yes 4096) words of ferrite core memory Each word was 39bits long, comprising two 19-bit instructions with a single modifier bit in the middle position that enabled instruction modification at run time.


The 803 had only a single address register to point at data and a single accumulator/register for all the processing to take place in.


There is a working example of an 803 at Bletchley Park