Re: Darwin & SMT?
Re: Darwin & SMT?
- Subject: Re: Darwin & SMT?
- From: Bernie Zenis <email@hidden>
- Date: Thu, 12 Sep 2002 21:46:23 -0400
On Thursday, September 12, 2002, at 08:57 PM, Niall Dalton wrote:
On Wed, 11 Sep 2002, Bernie Zenis wrote:
As far as I am aware, there has been no work done on the possibility of
removing speculative instruction execution, out of order instruction
execution, nor branch prediction in SMT processors. Some/All of those
There has been some work comparing an in-order and out-of-order
SMT processors:
S. Hily, A. Seznec `` Out-Of-Order Execution May Not Be Cost-Effective
on
Processors Featuring Simultaneous Multithreading '', IRISA Report No
1179,
March 1998, short version appears in proceedings of HPCA-5, Orlando,
Jan. 1999.
The report is available from
http://www.irisa.fr/caps/PROJECTS/Architecture/CacheArchitecture_US.html#
SECTION04
It comes down to the fact that if you are going for maximum throughput
and ready threads are available, then an in-order SMT gives almost
the same performance as an out-of-order SMT.
Last I heard, the SMT simulator is still Alpha only. Anyone been
working
on a PowerPC version?
SMTSIM is still Alpha only afaik. One other simulator worth checking out
is James Burns' (ex-USC, now with Intel) simulator that allows one to
explore the tradeoffs between SMT, chip-multiprocessor (CMP) and a mixed
SMT/CMP. It is based on SimpleScalar, which now also has a PowerPC
frontend. It may be possible, with sufficiently motivated hacking, to
come up with some version combining those..
I would assume that IBM's internal simulator - which _may_ be
available for academic usage - can simulate SMT PowerPC as this is due
for Power 5 I believe.
Thanks for the info. I'm not someone who is "in-the-loop." So I usually
just check
http://www.cs.washington.edu/research/smt/ occasionally for
new papers or new links to satisfy my curiosity for "What's new in SMT."
However, it seems to me that that site isn't the central location for
all things SMT as strongly as it used to be. SMT is just getting too
popular; darn! :-). If you have any other good places to look for SMT
activity, I'd appreciate knowing them.
-Bernie
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