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Antw.: Question on T9000



Hi Larry,
you should read as well the T9 Instruction Set Manual p.97ff.
Best rgds,
Uwe.

Gesendet mit meinem HTC

----- Reply message -----
Von: "Larry Dickson" <tjoccam@xxxxxxxxxxx>
An: "Occam Family" <occam-com@xxxxxxxxxx>
Betreff: Question on T9000
Datum: Do., Dez. 22, 2016 22:21


Hello all,

I don’t know who to address this to, so I will ask you all. Is there someone out there who worked on the T9000 protected mode system?

I picked up a copy of "THE T9000 TRANSPUTER HARDWARE REFERENCE MANUAL� at
http://www.transputer.net/ibooks/72-trn-238-01/t9000hrm.pdf
and looked at the communication instructions in, out, etc. (p 95). They were all marked P (Instruction not allowed in P-process). By contrast, move was marked M (Invalid memory-address for P-process), as were ldnl, stl, stnl, etc. Thus, the latter are legal given good addresses, and the former are not legal even if addresses are good, despite the famous CSP equivalence of

b := a

and 

chan c :
PAR
  c ! a
  c ? b

Why are the communications illegal? Was it because only one "current process� is allowed, or was it too hard to keep control over virtual memory while waiting for the second process, or was development effort too great for something which does not exist in C-language user-space? Was communication off-loaded to the L-process belonging to that P-process, or was it just not modeled?

By the way, thank you everyone who helped me to a copy of Michael Poole’s ETC paper in WoTUG-21. The book arrived, and has several other treasures besides ETC. For instance, “An optimizing multiprocessor occam system for the PowerPC� has true interrupt-level high priority, simple edge links, and even an extension of the configuration (.PGM) files!

Larry Dickson