Hyperthreading benchmarks on and off

[anvil82]

Can someone link me to some benchmarks of the p4c processors with HT enabled, and disabled.

I remember tomshardware had benchmarks when the HT cpus first came out, and it was faster with it disabled.

I run win2k with HT off, and wanted to know how much I was missing out on by not using winxp with HT on.

I don't want to use xp, but I will if the gains are significant.


Don't bother to reply with something like "HT and XP pwnz, use them".

Thanks

 

[archilochus]

Give this a try.I should be able to link you to others also.
THE FANMAN

LINK

OTHER LINK

 

[SLee]

http://forums.anandtech.com/messageview.cfm?catid=28&threadid=1180277&FTVAR_MSGDBTABLE=

By not using HT, you're generally losing >20% in performance everytime you run multi-threaded or multiple applications concurrently.

 

[Foxie3a]

I have no idea, but if it is a big enough thing to enable software acceleration into hardware that is designed for single CPU operation, then I would say that it is probably good stuff..

but what do I know...? lol

 

[bchur83]

Why do you run with HT off on win2k. It will work you know. win2k supports multi processors.

 

[anvil82]

Why do you run with HT off on win2k. It will work you know. win2k supports multi processors.

Only physical, not logical, it doesn't do much of anything on 2k.

 

[bchur83]

yes it does, it works just fine. It's just that XP is optimized a little better for HT. But HT works on 2k and shows better performance than with it off. The only thing you have to change is the HAL on the 2k system, which usually requires a reinstall, but I think there are other way to do it also through the device manager.

 

[batboy]

HT with Win2k works just fine. Not sure why people keep claiming it don't. You are definitely missing out on a little extra performance by not using HT.

 

[bchur83]

Thanks batboy for backing me on that one, I knew I wasn't dreaming things up.

 

[anvil82]

Explain this then:

http://www.intel.com/support/platform/ht/os.htm?iid=ipp_htm+os&

Why the heck would Intel tell people to turn it off in win2k if it would make it run faster?

The following desktop operating systems are not recommended for use with Hyper-Threading Technology. If you are using one of the following desktop operating systems, it is advised that you should disable Hyper-Threading Technology in the system BIOS Setup program:

Microsoft Windows 2000 (all versions)

Is there a better source than Intel on this matter?

 

[a12bc3]

That is some good proof dude

If you run XP Pro [which you don't] then definately turn it on, as it yields major boosts in performance when gaming, and video/mp3 stuff. Plus Pro is natively optimized for HTT, so regular surfin' and browsin' will be faster also.

 

[bchur83]

it still works and has better performance on win 2k. They may not recommend it, but it works just fine.

 

[batboy]

Intel also don't recommend us to overclock. Microsoft will do anything to make you buy another OS. They want everyone to make them rich by moving to XP. As soon as we do, they'll abandon XP and try to force us to buy the next version. Yes, XP is "optimized" a little more for HT, but Win2k still works fine.

I have Win2k Pro and early last summer I tried benching with HT enabled and with HT disabled. I can't find my notes, but there was a performance gain with HT enabled. I've used HT with Win2k now for 7 months and never had any problems. Win2k is rock solid stable and a great OS. I have no reason to switch to XP with a bloated code and forced authentication.

 

[Foxie3a]

You keep saying XT...

do you mean XP, or am I slow?

 

[batboy]

I just recently got a 9800 XT vid card, guess I mixed it up. It's Win XP, I'll edit my post, sorry.

 

[Foxie3a]

Well, come on..you started you, you gotta finish it..

how does the XT work in XP? ;-) lol

 

[batboy]

Like Tony says... GRRRRRRRRRRRREAT!

 

[larva]

I tested a 2.8c on an Asus P4P800 I built for a guy some months back on win2K and the hypertheading definitely didn't work correctly under 2K. My PCMark memory scores would plummet from ~10,500 to 8000 and the 3DMark2001 dropped from 17,200 to mid 15,000 area when hyperthreading was enabled. I thought there was something wrong with the machine or the windows, and I built a fresh win2K immediately and updated all aspects of it. HT still killed the performance when enabled.

My research of the subject told me nothing but that win2K and HT just don't work out for the majority of applications. Quake3 fps drooped also with it enabled, confirming the inhibitive effect on core performance indicated by the PCMark and 3DMark results. I'm not saying that win2k can't work correctly with HT, but I can confirm that it can go woefully wrong with win2K SP3 and 4.

 

[Foxie3a]

Do you think that Win03 does a better job?

 

[Albuquerque]

Hyperthreading results in a net loss of performance on Windows 2000 for these specific reasons:

Hyperthreading is NOT a seperate physical processor, and can only be used when there are seperate non-similar instructions that can be run in parallel. HT doesn't allow you to simultaneously compute two integer instructions, nor does it allow you to simultaneously compute two floating point instructions -- continue et al.

The problem here is that the multiprocessor HAL in Windows 2000 was specifically coded for only multiple physical processors. Because of that, the HAL is expecting two APIC processors being listed means that two of ANY instruction can be run parallel. As such, it schedules and tasks things simultaneously that cannot be run that way by a HT processor. XP's multiprocessor HAL was coded to detect the processor type, and has seperate functionality for HT-enabled processors versus true multiple processors.

The caching structure, to include instruction prefetches and data trace cache on the x86-HT processors don't perform well if they are being addressed like a true multiprocessor part. They can only do unlike instructions in parallel, and they must be dispatched and paired in a certain way to get the most gain while causing the least amount of cache misses.

Can you enable HT in Windows 2000? Sure, I think it is configurable and useable after Service Pack 3. Does that mean it will actually result in performance gain? It's much more likely NOT...