HT and W2k

[luisfreak]

Hello Everybody.
I recently put together a Pentium 4 box. I put a 3.0 Prescott in it (with Hyper Threading). What I did not realize was that by default, the BIOS in my motherboard disables Hyper Threading. So I installed Windows 2000 with the hyper threading disabled. Now, when I try to enable hyper threading through the BIOS, windows 2000 does not recognize it.
Is there a way to enable HT? or should I just switch to a HT enabled OS?
Does the fact that w2k does not recognize Hyper Threading have anything to do with the fact that I did not enable it while I was installing the OS? or is it that there is no way to enable HT in w2k?

Thanks for your help!

 

[spyordie007]

Win 2k doesnt support hyperthreading, if you had enabled it in the bios while installing windows it would have believed them to be 2 seperate physical processors.

Unless you want to run XP you're better off just leaving it disabled.

 

[luisfreak]

Now, here is another question.
Is it worth switching to XP just to get the benefit of HT? am I going to see a performance leap?
what about Linux? is it a good "HT Performer"?

Ok, that was 4 questions....

Thanks

 

[spyordie007]

I wouldnt say "a performace leap"; I've heard that some multi-threaded applications can get an extra 10-20% if running on a HT system.

Single-threaded applications (as most desktop applications/games are) you wont see any improvement in performance (and technically it would be possible to see a reduction in performace in those applications while the OS loads other processes on the 2nd logical CPU robbing resources from the 1st which is running your application).

EDIT: missed your other questions.
If HT is the only thing you care about than XP probably isnt going to make much a differance. Personally I wouldnt spend the money on the upgrade for HT alone, but if there are other advantages than I would.

Yes most all recent versions of Linux will support HT.

 

[kylef]

Win2k will use both logical processors, but the problem is that you're using the wrong HAL and the wrong kernel.

When Win2k setup does its hardware inspection, it figures out how many cpus you have and installs either the ACPI PC or ACPI Multiprocessor PC HAL. It also chooses which kernel to copy over from the install CD (ntoskrnl.exe or ntkrnlmp.exe, the MP kernel).

Right now you've got the wrong kernel binaries installed for MP support.

And technically spyordie is correct, Win2k doesn't really understand the difference between a logical cpu and a physical cpu, so there are performance issues in Win2k when you have a single thread running full-out and nothing else going on. But as long as you have multiple real threads running, Win2k can use the HT processors just fine, with a significant perf boost over a single proc system. (It's just when one proc is executing a thread and the other is in the idle loop where perf takes a hit.)

 

[spyordie007]

But as long as you have multiple real threads running, Win2k can use the HT processors just fine, with a significant perf boost over a single proc system.

It's important to note here that the performance improvement is going to be in total system performance across all threads. However single-thread performance (of which most desktop users are primarily concerned) will only get reduced.

 

[yelo333]

Originally posted by: kylef
Win2k will use both logical processors, but the problem is that you're using the wrong HAL and the wrong kernel.

When Win2k setup does its hardware inspection, it figures out how many cpus you have and installs either the ACPI PC or ACPI Multiprocessor PC HAL. It also chooses which kernel to copy over from the install CD (ntoskrnl.exe or ntkrnlmp.exe, the MP kernel).

Right now you've got the wrong kernel binaries installed for MP support.

And technically spyordie is correct, Win2k doesn't really understand the difference between a logical cpu and a physical cpu, so there are performance issues in Win2k when you have a single thread running full-out and nothing else going on. But as long as you have multiple real threads running, Win2k can use the HT processors just fine, with a significant perf boost over a single proc system. (It's just when one proc is executing a thread and the other is in the idle loop where perf takes a hit.)

Are you saying installing 2000 w/ HT switched off, and then switching it on after install would help w/ the performance problems?

 

[kylef]

Originally posted by: spyordie007

But as long as you have multiple real threads running, Win2k can use the HT processors just fine, with a significant perf boost over a single proc system.

It's important to note here that the performance improvement is going to be in total system performance across all threads. However single-thread performance (of which most desktop users are primarily concerned) will only get reduced.

Correct about single thread perf. Technically, however, that is true on XP and S2k3 also with HT, so that is why I didn't mention it here.