Introducing the new PC Quattro from ICL

The multi-user ICL Quattro - so-called because it could support up to four users - was a development of the RAIR Black Box - the machine which ICL had already used as its first "ICL PC". It seems to show that ICL just couldn't shake off its multiuser heritage.

ICL was the part-nationalised company that had been set up by Harold Wilson in 1968 - it was the end result of mergers of all sorts of famous British computer names, like Marconi, English Electric, Leo and bits of Elliot. 

The Quatto ran Intel's 8086-2 - confusingly not the same as the 80286, but a "go-faster" version of the older 8086, being run at its limit of 8MHz[source: https://www.cpu-world.com/CPUs/8086/Intel-D8086-2.html]. 

Making use of this was CP/M-86, which via a merger with MP/M had by now been re-branded as Concurrent DOS, to try and counter Microsoft's domination of the 16-bit computer market. 

Normal CP/M-86 could support up to four concurrent processes, but thanks to it multi-user MP/M heritage it could manage 16 - four for each of the four users.

Concurrent DOS was actually a version of Concurrent CP/M but which had implemented a "PC mode", which was meant to give some compatibility with IBM software. However, PC Mode wasn't present in the version running on the Quattro - all it could do was read IBM-format disks.

In a benchtest in December 1985's PCW, Nick Walker concluded:

~"The market for multi-user micros is still very much an open market, with no definite trends at the moment. With an inovative produce ICL might have been able to capture some of this market. Sadly the Quattro is not such a product, being little more that yet another development of the RAIR Black Box using some of the rarer boards. The Quattro will take its place with previous ICL PCs, selling to corporate buyers who already use ICL mainframes. It's particularly disappointing given that the Quatrro is being pushed as the machine with lots of ICL in-house innovation"[source: Quattro benchtest, PCW, December 1985, p0. 176-182].