question about Intel P4 versus Alpha's

Dominic Wu dwu at swales.com
Thu Jan 9 20:26:35 EST 2003



 -----Original Message-----
From: 	beowulf-admin at beowulf.org [mailto:beowulf-admin at beowulf.org]  On
Behalf Of Daniel Kidger
Sent:	Thursday, January 09, 2003 4:57 AM
To:	'Henderson, TL Todd'; 'Patrick Geoffray'
Cc:	'beowulf at beowulf.org'
Subject:	RE: question about Intel P4 versus Alpha's


Not quite true - the giveaway about hyperthreads is if 'top' shows twice as
many lines starting with 'CPU' than you have real cpu's. (You can get the
same info from /proc/cpuinfo).

In general, people prefer to switch off hyperthreading for HPC clusters,
either via a BIOS option, or by passing 'noht' to the kernel (in say
grub.conf).

I think that it was the P4 Xeon Prestonia that was the first that had
hyperthreading. It started at 1.8GHz

Yours,
Daniel.

--------------------------------------------------------------
Dr. Dan Kidger, Quadrics Ltd.      daniel.kidger at quadrics.com
One Bridewell St., Bristol, BS1 2AA, UK         0117 915 5505
----------------------- www.quadrics.com --------------------


-----Original Message-----
From: Henderson, TL Todd [mailto:Todd_Henderson at isl-3com.com]
Sent: 08 January 2003 19:49
To: 'Patrick Geoffray'
Cc: 'beowulf at beowulf.org'
Subject: RE: question about Intel P4 versus Alpha's


These are P4 2.4 ghz and I didn't find anything in the bios about it.  I
thought I had read on Intel's website that hyperthreading was only in the
3.xx ghz P4's?

Todd


-----Original Message-----
From: Patrick Geoffray [mailto:patrick at myri.com]
Sent: Wednesday, January 08, 2003 1:38 PM
To: Henderson, TL Todd
Cc: 'beowulf at beowulf.org'
Subject: Re: question about Intel P4 versus Alpha's


Hi Todd,

On Wed, 2003-01-08 at 10:49, Henderson, TL Todd wrote:
> 95-100%cpu utilization range.  However, now we have a cluster of P4's and
> when I look at top, it is more like 70-80% cpu usage.  This is using the
> same number of cpu's, the same switch, same code, and same problem for the
> code.  The jobs are still completing in about 30-40% less time, so we are
> getting a speed up.

Is Hyper-threading enabled ?

Patrick
--

Patrick Geoffray, Phd
Myricom, Inc.
http://www.myri.com
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