From:	root AT jacob DOT remcomp DOT fr (root)
Subject:	Re: High resolution clock
26 Jul 1997 01:17:26 -0700 :
Approved:	cygnus DOT gnu-win32 AT cygnus DOT com
Distribution:	cygnus
Message-ID:	<m0ws1Hp-000ALGC.cygnus.gnu-win32@jacob.remcomp.fr>
Original-To:	joerg AT std DOT saic DOT com (Joerg Lepler)
Original-Cc:	gnu-win32 AT cygnus DOT com
In-Reply-To:	<Pine.SOL.3.96.970725211029.26675C-100000@jade1> from "Joerg Lepler" at Jul 25, 97 09:22:39 pm
Original-Sender:	owner-gnu-win32 AT cygnus DOT com

> 
>    Presently I am trying to do fine grain network performance measurments.
> Therefore I would need some functions for high resolution clocks. I
> remember that on a SUN or a SGI there were sw clocks with a resolution as
> low as 108 nanoseconds. As I have to deal with latencies of 2-3
> milliseconds, I need a clock with a resolution of at least one
> millisecond. 
> 
> Does anyone know about such clock functions for the win32 environment?
> 

If you are using a pentium, the best clock is the time stamp counter of the
CPU. This clock is incremented every clock cycle. If you are using a new
CPU at, say 200MHZ, you have a clock that is incremented 200 millions times
each second!

If you use the 'lcc-package', you can use the 'rdtsc' intrinsic that will
generate a floating point number containing the 64 bit rdtsc value. Under
GNU you will have to code that in assembler. I do not know for sure if the gnu
assembler supports rdtsc, but I believe it does.
	rdtsc leaves a 64 bit value in EAX EDX.
regards

-- 
Jacob Navia	Logiciels/Informatique
41 rue Maurice Ravel			Tel 01 48.23.51.44
93430 Villetaneuse 			Fax 01 48.23.95.39
France
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