Re: Windows 2003 Enterprise Hyperthreading w/ 8 procs
From: Scott LaFave (slafave_at_trendmls.com)
Date: 09/02/04
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Date: Thu, 2 Sep 2004 12:19:15 -0400
We fixed this by re-loading the OS with all processors installed and
hyperthreading enabled. The machines now see all 16 logical processors.
BUT...it seems like this is not a true solution. As long as you have the
multi-proc kernel loaded already, Windows is supposed to pick up new
processors when it boots up, and it has in the past for us with no issues at
all. Having to reload is inconvenient, to say the least.
I don't know if this was an issue because of hyperthreading or the high
number of processors involved. I also don't know if the fault was with HP
or MS or both. At least we fixed it though.
BTW, we have an open case with MS. The Windows setup support rep insisted,
rather heatedly, that 2003 Enterprise could not see more than 8 processors,
logical or otherwise. When we pointed him to the MS documentation saying
that it was supposed to be able to see 16, he said he would have to get back
to us. We plan to send him a screen shot of task manager showing 16
processors running. :-)
"Scott LaFave" <slafave@trendmls.com> wrote in message
news:OxrmngGkEHA.3724@TK2MSFTNGP11.phx.gbl...
> We just purchased an HP DL740 server that came installed with 4 procs.
> The procs are hyperthreaded (HT), for a total of 8 logical procs. We
> installed 2003 Enterprise and it picked up all 8 logical procs just fine.
>
> After the OS install, we purchased and installed another 4 HT procs, for a
> total of 8 physical/16 logical procs. The system bios reports all 8
> physical procs as present and that HT is enabled. However, Windows still
> only reports 8 procs.
>
> The white paper "Windows Support for Hyper-Threading Technology" located
> at
> http://www.microsoft.com/whdc/system/CEC/HT-Windows.mspx
> says that 2003 Enterprise supports 8 physical/16 logical procs.
>
> Under
> "HKLM\System\CurrentControlSet\Enum\ACPI\GenuineIntel_-_x86_Family_15_Model_2"
> there are 12 proc keys enumerated, "_0" to "11". Unfortunately, I do not
> know how many procs were enumerated before we installed the extra 4. Two
> other machines, each with 2 HT procs, have 4 keys enumerated here. My own
> workstation is running XP with 1 HT proc and it has 2 keys enumerated. It
> seems to follow there is one key per detected logical proc. However, if
> we disable hyperthreading on this new server, the keys do not drop to 8 as
> I might have expected them to.
>
> Has anyone else observed this behavior? Does anyone have any ideas as to
> why 2003 Enterprise will not recognize logical processors past 8?
>
> Thanks!
>
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