Win2K Pro -- Hyperthreading with dual Xeons

[R. J. Salvi]

Has anyone tried Win2K Pro on a dual Xeon box with HT enabled. If so, does
it see both the physical and logical processors? Thx.

 

[Rob Stow]

Has anyone tried Win2K Pro on a dual Xeon box with HT enabled.

Many of us have.

If so, does
it see both the physical and logical processors? Thx.

HT makes each physical processor appear as two logical processors
to W2K or NT.

W2K Pro can only use two processors and hence ends up using only
the first logical processor on each physical processor. The net
effect is a minor performance penalty.

Even W2K Server - which can use all four logical processors -
takes a bit of a hit.

I would recommend you disable HT. MS says the same thing.


My own question: I haven't tried W2K3 Server on a dualie with HT
enabled. Can anyone tell if W2K3 Server can take proper
advantage of HT ?

 

[Leythos]

My own question: I haven't tried W2K3 Server on a dualie with HT
enabled. Can anyone tell if W2K3 Server can take proper
advantage of HT ?

I have it running on Dual Xeon's and 2003 Standard Server here in my
house - seems to scream in relation to all my other systems. I almost
never see more than 5% load on any of them.

 

[R. J. Salvi]

Many of us have.


HT makes each physical processor appear as two logical processors to W2K
or NT.

W2K Pro can only use two processors and hence ends up using only the first
logical processor on each physical processor. The net effect is a minor
performance penalty.

Even W2K Server - which can use all four logical processors - takes a bit
of a hit.

I would recommend you disable HT. MS says the same thing.

Thanks Rob. I was under the impression that since WinXP Pro also has a two
CPU license and is built on the Win2K platform, there might be a possibility
of 2K recognizing both physical and logical CPUs. Is ir correct to assume
that that HT is part of a kernel mode instruction set?...and WinXP's differs
from Win2K's?

 

[Rob Stow]

Thanks Rob. I was under the impression that since WinXP Pro also has a two
CPU license and is built on the Win2K platform, there might be a possibility
of 2K recognizing both physical and logical CPUs. Is ir correct to assume
that that HT is part of a kernel mode instruction set?...and WinXP's differs
from Win2K's?

Before SP1, XP didn't deal with HT any better than W2K did.
I have no idea what MS had to put into SP1 to tune XP for HT.

I suppose MS could have done the same thing with W2K, but I'm
sure they simply decided W2K is yesterday's OS - if customers
want the new features, they have to buy the new OS. Not much
different from MS's rationale to not add USB and IEEE1394 to NT4.