The IBM Mainframes were a 3084, 3090-600J, System 36 & 4341. The main processing was performed on the 3090. The ICL’s were Series 39’s.
The IBM’s and ICL’s lived on different floors @ 330 Spencer Street.
Now the official word as to why we had the biggest ICL Mainframe complex in the Southern Hemisphere, was this:
IBM Mainframes are good for batch processing. ICL Mainframes are better at online transactional processing (ie. bank branch transaction processing).
The unofficial, or as I like to say, real reason was rumoured to be this:
One night, the ICL On-site Engineer2 was on the IBM floor, and noticed the ICL “J” scheduler program running on one of the IBM 4341 mainframes. He reported this to ICL Management. An SBV programmer had ported the “J” scheduler to the IBM Mainframe. Clever bit of programming it seems.
“Discussions” occurred between SBV IT & ICL Management.
Costly legal action avoided, and SBV became the largest ICL Mainframe operator in the Southern Hemisphere.
1. The Mainframe floor was derisively called “Heaven” by the SBV ICL Mainframe Operators, as the IBM floor was one floor above them.