From: "Russ Cox" <rsc@plan9.bell-labs.com>
To: 9fans@cse.psu.edu
Subject: Re: [9fans] bochs still no go
Date: Mon, 10 Dec 2001 22:25:43 -0500 [thread overview]
Message-ID: <20011211032545.43452199B5@mail.cse.psu.edu> (raw)
> If "RDMSR" is being used to read the time stamp counter,
> it should be replaced with RDTSC (0x0F 0x31). RDMSR is
> a much slower instruction.
That's not at all clear. I bet they're approximately
the same on real hardware. RDMSR is much slower under
VMware because it requires trapping into the VMware
runtime, while RDTSC, an unprivileged instruction, does not.
Since Bochs isn't using the underlying machine to
execute _any_ instructions natively, I would be
hesitant to draw speed comparisons. Of course,
it appears that RDMSR is unsupported, but that's
different. We use RDMSR for things other than
reading the time stamp counter, though.
Russ
next reply other threads:[~2001-12-11 3:25 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-12-11 3:25 Russ Cox [this message]
2001-12-11 8:01 ` Mike Haertel
-- strict thread matches above, loose matches on Subject: below --
2001-12-10 22:19 Matt
2001-12-10 23:35 ` Mike Haertel
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