[THIN] Re: Hyperthreading

  • From: Thin Fan <thinfan@xxxxxxxxx>
  • To: thin@xxxxxxxxxxxxx
  • Date: Thu, 30 Sep 2004 10:34:15 -0700

See this note:

Windows 2000 Server does not distinguish between physical and logical
processors on systems enabled with Hyper-Threading Technology; Windows
2000 simply fills out the license limit using the first processors
counted by the BIOS. For example, when you launch Windows 2000 Server
(4-CPU limit) on a four-way system enabled with Hyper-Threading
Technology, Windows will use the first logical processor on each of
the four physical processors, as shown in Figure 2; the second logical
processor on each physical processor will be unused, because of the
4-CPU license limit.

It seems to indicate that it's simply a 'Licensing Limit' of CPU's as
the only reason that it won't see the additional.

All interesting stuff :)




On Thu, 30 Sep 2004 10:31:43 -0700, Thin Fan <thinfan@xxxxxxxxx> wrote:
> Yes I actually linked to that in my follow on.
> 
> To me it confuses matters worse as it seems to indicate that the only
> reason a 4-Way Server won't see the additional logical processors is
> due to the CPU License Limit in Standard vs Enterprise Server.
> 
> But it doesn't really provide an example of what happens on Dual CPU
> HT's.  Until it gives the example on the .net (Wk23) server at the
> end.
> 
> Still leaves the issue a little vague really.
> 
> 
> 
> 
> ----- Original Message -----
> From: Jim Kenzig http://thethin.net <jimkenz@xxxxxxxxxxxxxx>
> Date: Thu, 30 Sep 2004 10:23:50 -0700 (PDT)
> Subject: [THIN] Re: Hyperthreading
> To: thin@xxxxxxxxxxxxx
> 
> Hmm did you see the link for Microsoft about using HT on Windows
> Servers on that page?
> http://download.microsoft.com/download/e/2/3/e239dd00-9ae1-41a9-bb3f-c01f658d16b1/hyperthreading.doc
> 
> JK
> 
> Thin Fan <thinfan@xxxxxxxxx> wrote:
> 
> Those links from Intel were for Desktop Processors though. There is a
> seperate information page for Xeon HT's for servers.
> 
> Xeon Information: http://www.intel.com/design/Xeon/
> 
> Very interesting discussion though. Personally I have not disabled HT
> on those Xeon Servers that we support.
> 
> Even on our latest VM Servers I have left it on as VMWare ESX 2.x now
> can see "HT". Whether it actually utilizes HT is another question.
> 
> ----- Original Message -----
> From: Jim Kenzig http://thethin.net
> Date: Thu, 30 Sep 2004 07:06:52 -0700 (PDT)
> Subject: [THIN] Re: Hyperthreading
> To: thin@xxxxxxxxxxxxx
> 
> See
> http://www.2cpu.com/articles/42_1.html
> http://thethin.net/faqs2.cfm?id=444&category=1&sortby=score
> Leave it off for Win2K!
> http://thethin.net/faqs2.cfm?id=443&category=1&sortby=score
> 
> Regards,
> Jim Kenzig
> http://thin.net
> 
> Bob wrote:
> Has anybody experimented with Hyperthreading On -vs- Off on Win2k
> servers? I've heard rumblings that it can be problematic, and perhaps
> decrease performance. I noticed that most SpecInt. winners have it
> disabled. I'm considering disabling it on one of my farm servers to
> observe the results. If anybody else has experimented I'd love to
> hear about it.
> 
> Thanks in advance,
> Bob
>
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