Reply to post: Re: Now I wonder when someoen will port the ICL 2900 architecture and George 3

Multics resurrected: Proto-Unix now runs on Raspberry Pi or x86

Deryk Barker

Re: Now I wonder when someoen will port the ICL 2900 architecture and George 3

Which?

George 3 ran on 1900 machine, the 2900s ran VME/B (and wasn't there a smaller VME/K?)

The ICL people visited the Multics people during the design phase, but IIRC the Multics people couldn't understand why the ICL people felt that 32 rings were needed. Multics had originally had 64 on the GE-645, but this was reduced to 8 on the 6180 - and only rings 0,1, 4 and 5 were actually used initially although later on something (was it forum?) ran in ring 2 and some of the UK Rainbow book networking software ran in ring 3 (I know this for certain, as I wrote a call gate for the latter). Rings 6 and 7 were sometimes referred to as "outer darkness" as the standard software was not accessible in those rings.

Of course, the 2900 could emulate the 1900. Indeed, in the early 1980s my wife encountered, at BT in South Wales, the "orange Leos" which were ICL 2900s running the 1900 emulator running the System-4 emulator running the LEO emulator running LEO programs for which they no longer had source code.

POST COMMENT House rules

Not a member of The Register? Create a new account here.

  • Enter your comment

  • Add an icon

Anonymous cowards cannot choose their icon

Biting the hand that feeds IT © 1998–2019