Messages in this thread |  | | Date | Mon, 17 Sep 2001 19:19:31 +0200 (CEST) | From | Jean-Marc Saffroy <> | Subject | Re: [Q] Implementation of spin_lock on i386: why "rep;nop" ? |
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On Mon, 17 Sep 2001, Dave Jones wrote:
> On Mon, 17 Sep 2001, Jean-Marc Saffroy wrote: > > > What is the intent behind this "rep;nop" ? Does it really rely on an > > undocumented behaviour ? > > Its used to stop Pentium 4's from cooking themselves. > See the P4 manuals for more info.
Ok, I found it: actually it is the PAUSE opcode in the P4 instruction set, and the doc for PAUSE mentions that it is equivalent to a NOP on older IA-32 processors.
So no black magic here, except that "rep;nop" is a bit misleading, since the Intel docs for REP and NOP do not mention PAUSE...
Thanks all for you help.
Regards,
-- Jean-Marc Saffroy - Research Engineer - Silicomp Research Institute mailto:saffroy@ri.silicomp.fr
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