P4 and Hyperthreading

Vann H. Walke vann at walkeonline.com
Sat Jan 11 15:47:15 PST 2003

IBM Developer Works has a new article examining the effect of
Hyper-Threading in Linux:



On Sat, 2003-01-11 at 18:06, Steve_L_Smith at dell.com wrote:
> Just to clarify:
> Hyperthreading was introduced in the Prestonia version of the  Xeon
> processor, January 2002 I believe. This is the 13micron device rather than
> the previous Foster 18micron device. Speeds overlapped at launch, Xeon
> Prestonia was launched at I think 1.8, 2 and 2.2GHz, and Foster processors
> co-existed for a while. At this time the only products shipping with Xeons
> were workstation class products using the Intel 860 chipset - all server
> class products (e.g. those based on Intel 7500 and Serverworks GC class
> chipsets) came later and use Prestonia Xeons.
> Recently Intel have also incorporated Hyperthreading on Pentium 4. The
> confusion arises partly because of Intel's Pentium 4 and Xeon nomenclature.
> To be incredibly pedantic (sorry:-) the Pentium 4 is a single processor
> device, it has no ability to work in an SMP machine. The Xeon (note it is
> Xeon, not Pentium 4 Xeon) is the multi-processor variant of the Pentium 4,
> that is, it contains additional on-chip logic to allow it to work in an SMP
> machine (subject to an appropriate chipset). Note that there is no such
> thing as a Pentium 4 Xeon, unlike the Pentium III Xeon (also note the change
> from Roman to Arabic numerals).
> So - you can have a single processor system based on Pentium 4, you can have
> a single processor system based on Xeon (i.e. a system with only one Xeon
> processor in it (although there is not a lot of point)), and a
> multi-processor system of Xeons. Just to complete (and confuse further) the
> picture, there is also a device called the Xeon MP. This is a Xeon processor
> designed for 4-way and up SMP systems, containing larger caches but slower
> clock speeds. This device is still (at least I believe so) based on Foster
> (18 micron) technology but does include Hyperthreading.
> If anyone out there from Intel could confirm or add to this I'm sure we'd
> all appreciate it.
> So there you have it!
> Steve
> -------------------------------------------------
> Steve Smith
> HPC Business Manager
> Dell EMEA
> Dell Campus, Cain Road, Bracknell, RG12 1FA, UK
> Direct: +44 1344 372037
> Switchboard: +44 1344 812000
> Fax: +44 1344 372359
> Mobile: +44 7802 594874
> email: steve_l_smith at dell.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
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