Windows 2000 and HyperThreading

[MDE]

I've heard stories about Windows 2000 and HyperThreading being both a nightmare and working like a dream. Anyone that has tried it, please give me some feedback as I have an odd itch to go back to 2000 for some reason, but I don't want to kill my F@H production by having to disable HT.

 

[n0cmonkey]

According to Virtual Larry in the winxp vs 2k thread on the front page, as long as you have sp4 it should be supported just fine.

 

[Canterwood]

I couldn't vote, because I would have to say that yes it does work, but some applications can take a serious performance hit, whereas some will perform much better.
Its defintely not as optimized as it is on XP, but it wont crash your system or anything.
I've found that most games take a performance hit with HT enabled on Win2K, whereas you can get a good performance boost in say 3dMax with HT on.
I'd say test your applications with HT on and off and see what it performs like, then make your choice.

 

[Auric]

To quote meself in regard to CPU usage during WMV-HD decoding:

"Welp, I'm trying out XP now and the HT is making a significant difference with my "P2.9". Instead of 70-90% usage with the fastest Overlay Mixer it is down to 40-60% (averaging 50%) with any output mode including the slowest VMR9."

I never noticed any disadvantage to having it enabled with 2000 but didn't notice any advantage either.

 

[Nothinman]

It works fine, but the performance won't be as good as XP because Win2K can't discern between logical and physical CPUs.

 

[THUGSROOK]

no, it doesnt work correctly.

 

[spyordie007]

Technically it doesnt "work" at all, saying it works would imply that it is doing what it is supposed to be doing and under 2000 that is simply not the case. For it to "work" correct the OS must know the differance between logical and physical processors; 2000 simply does not have this capability.

Will 2000 run on a HT CPU? Absolutly, and you shouldnt have any stability issues.
But that doesnt mean hyperthreading is "working" like its supposed to.

Yes there were some 2000 SP4 updates that helps the scheduler get along better, but it doesnt address the additional licensing issues. I disagree with virtual larry's answer on the xp vs. 2000 thread because he assumes that because microsoft says the scheduler is supposed to work better that it is supported and this is simply not the case.

Anyway, this issue has been discussed to death in plenty of other threads.

 

[VirtualLarry]

Originally posted by: spyordie007
Technically it doesnt "work" at all, saying it works would imply that it is doing what it is supposed to be doing and under 2000 that is simply not the case. For it to "work" correct the OS must know the differance between logical and physical processors; 2000 simply does not have this capability.

Will 2000 run on a HT CPU? Absolutly, and you shouldnt have any stability issues.
But that doesnt mean hyperthreading is "working" like its supposed to.

Yes there were some 2000 SP4 updates that helps the scheduler get along better, but it doesnt address the additional licensing issues. I disagree with virtual larry's answer on the xp vs. 2000 thread because he assumes that because microsoft says the scheduler is supposed to work better that it is supported and this is simply not the case.

Anyway, this issue has been discussed to death in plenty of other threads.

Well, I was presenting the facts straight from MS and Intel. If you don't believe those are accurate, I would like to find out why. Note that "properly supports" does not mean "optimized for", nor "guarantees a performance increase". Those largely depend on the types of tasks in question being run on the HT machine. There are certain categories of tasks, that HT cannot ever improve the performance of, no matter how you tweak the OS scheduler. There are also tasks that can benefit highly from HT, but the performance optimization that you see can be slightly tempered by the OS. But what I pointed out in the other thread, is that W2K does implement all of the necessary guidelines specified by Intel, for HT to "work". The only major difference, is the licensing issue, and that isn't even a technical issue at all.

Personally, I think that you mis-understand how HT "works", and how Intel specifically designed it to operate as a functional drop-in replacement for SMP-compatible x86 systems. If you somehow inferred that whether an HT system gives a performance increase, determines whether it is "working" or not, then you should go back and read the Intel technical whitepapers a bit more carefully, as HT can actually lead to decreases in performance. (As was show in the benchmark graphs on that article that I linked from TechReport, running on XP SP1. So with HT enabled, and even more with the update patch from MS to "fix" HT support, the benchmark results were *worse*. So do you also believe that HT "doesn't work" on XP SP1, even with an MS patch specifically to fix HT support?)

 

[spyordie007]

I disagree. I would consider a neccisary "feature" of any OS that supports HT the ability to differentiate between a physical and a logical processor which 2000 simply does not have the capability. This can become a big issue on multi-way HT systems (i.e. Windows 2000 Server running on a quad p4 HT system) because the OS's scheduler will still schedule threads to virutual CPUs while keeping other physical CPUs idle because it doesnt know the differance. This can lead to a decrease in performance that you wouldnt otherwise have if you were running an OS that properly supported it such as 2003 server.

So again yes you can run Windows 2000 on a HT CPU, but no the OS does not properly support it and therefore does not "work" like HT is designed to.

Also if you think the licensing thing isnt an issue go and try installing 2000 Pro on a dual-HT machine.

I have a pretty good idea how HT works, I just think we have a bit differant definition on the word "works"

 

[Steve]

So, does 2000 show two physical CPUs, or is it one physical and one virtual, post-SP4?

 

[spyordie007]

Originally posted by: sm8000
So, does 2000 show two physical CPUs, or is it one physical and one virtual, post-SP4?

Regardless of what SP you're running Windows 2000 believes a single HT CPU is 2 seperate physical CPUs.

 

[Nothinman]

Regardless of what SP you're running Windows 2000 believes a single HT CPU is 2 seperate physical CPUs.

For now...

 

[Auric]

It's just a matter of moolah. In general, 5.1 could easily have been a free upgrade to 5.0 and they still could have made most of the potential upgrade profits from the 4.0 OT to 5.1 NT "lite" (aka XP Home) which was the main point of XP (to split NT). Serious bidnesses were already using 5.0 and did not jump to "upgrade" to 5.1. I assume 2003 Server (with HT) is "the designated path" from the significant 2000 money (i.e. server as opposed to client).

 

[Unforgiven]

i run folding @ home on 2 p4's with HT enabled on windows 2000 sp3 & sp4 and have no issues at all.

 

[Canterwood]

Originally posted by: Nothinman

Regardless of what SP you're running Windows 2000 believes a single HT CPU is 2 seperate physical CPUs.

For now...

Are you suggesting that a future Service Pack/update will make Win2K HT fully HT aware?

I can't see it happening.

 

[Nothinman]

Are you suggesting that a future Service Pack/update will make Win2K HT fully HT aware?

I have no insider knowledge but I'm suggesting that it would be possible and I can't see why MS doesn't do it. Unless their process scheduler is too complicated to maintain it should be hard to retro-fit knowledge to discern CPU types, it was done for Linux.

 

[drag]

I doubt it.

Doesn't seem like MS to give anybody any reason to stick with a older OS when they can make buying a new OS more attractive by simply not doing something. Gamers want HT support on their systems for whatever reason, if they realy want it then they have to be running XP.

Why put the extra effort into reducing the incentive to upgrade? They are already announced that they are not going to retrofit several newer security measures that they introduced with XP SP2 to older stuff.