24 Oct
2005
24 Oct
'05
12:51 p.m.
Tony Duell wrote:
NO, just for fun... I doubt very much I could improve on the
performance for running the VAX instruction set. I have not looked at
the prints carefully enough to determine how much of the instruction
set is hard-wired (if any), I wonder if it would be possible to run a
different instruction set entirely.
I don't have an exact reference to hand, but one of the
"how we built VMS for the uVAX-II" articles in one of the
DEC Technical Journals describes how they made a VAX-11/730
behave as a (then only proposed) MicroVAX-II. They did this
to check the performance (and correctness) of the subsetting.
The 730 was chosen because it was entirely soft.
SO I guess you could make it do almost anything within
reason. Perhaps it could have been a faster PDP-8 than
the PDP-11/60 ... or given the 730's reputation, perhaps not :-)
Antonio
--
Antonio carlini
arcarlini at iee.org
The 11/730, of course, is mostly PALs (as I said) with
some RAM as a
control store, 8 off 2901s as the ALU, and an 8085 (I think) to
load the control store, etc. One day I am going to look into
modifying the microcode of that machine...
To what end? Increased performance?