Off topic: ICL 1904A and ACTP

[Peter Tomlinson]

Although this is off topic, I hope that you will bear with me.

It is 40 years ago that the ICL 1904A mainframe first burst into life. 
Conceived by ICT in 1966 and surviving across the merger to become a 
money-spinner (also in 1904X and 1904S variants), its gestation was 
greatly aided by the synchronous logic simulation system developed by 
Charles Lindsey, using the Manchester University Atlas. I well remember 
a long period when every working day I coded up instruction sequences as 
a colleague created them (he having unfortunately first discovered that 
the so-called Large Machine Addressing Modes and Order Code were not 
exactly defined mathematically), then a young lady working for Charles 
(she an immigrant from eastern Europe, I believe - they were with us 
then) prepared a daily and highly accurate update paper tape (from my 
handwritten script) for the next update of the design description, and 
that was taken down to the Atlas computer suite for an overnight run, 
following which (if the Atlas had not crashed, or, if it did, the 
operators found time to have another 45 minute run for us) someone had 
to collect the line printer output and get it back to West Gorton for 
checking and then the daily cycle started again. We didn't simulate 
everything (so the team designing the floating point unit gave 
themselves a hard time), but later we did simulate the optional Memory 
Management Unit. And it was all put to bed by August 1968. George 4 to 
make use of the MMU took a while longer...

The development of the simulation system was funded by a grant from the 
govt's Advanced Computer Techniques Project.

Those were the days when civil servants understood what their money (our 
money) was being used for, but it didn't last much longer in a number of 
fields.

Peter