Will Win2K ever support HT?

[Goi]

Right now apparently only WinXP and perhaps .NET/Win2K3 supports Hyper Threading. I'm wondering if the new Win2K SP4 will add HT support, and if not, are there any plans for HT support in Win2K? MS might have dropped Win98/ME support, but not Win2K yet right?

 

[AndyHui]

Windows 2000 does support HyperThreading, although not fully. You would need to make a lot of changes to the process scheduler, which would mean a major overhaul of the OS.

 

[Goi]

Hmmn, I didn't know about that. Everywhere I've read says that Win2K doesn't support HT. Can you elaborate on its partial HT support status? What does it support specifically and what doesn't it support? Does "major overhaul" mean something that would probably not be fixed with a Service Pack?

 

[SaigonK]

2k does support hyperthreading.
It is quite interesting to see it when you buy a server with 2 CPU;s and task manager shows up as having four.

 

[Goi]

Doh...that certainly is news to me. I've always thought that Win2K doesn't support HT, and in a couple of forums I've read that as well.

 

[sciencewhiz]

Win2k sees a HT CPU as two real processors. This is a problem because it will try to schedule two tasks trying to do the exact same type of operation. WinXP+ sees a physical CPU and a "logical" CPU and schedules different types of tasks for each.

In some cases, Win2k will run faster with HT, and sometimes slower, depending on what tasks it's doing. WinXP and newer *should* at worst run no slower then a single CPU and often faster.

 

[AndyHui]

HT is actually "useable" on Windows 2000.

Windows 2000, unlike Windows XP, will recognise a HyperThreaded processor as two separate physical processors. Windows XP will recognise an HT CPU for what it is: two logical processors.

The difference is that supposedly WinXP will do a little better at process scheduling, so that threads minimise clashing for CPU resources. Windows 2000, seeing two processors, is going to really treat it as two separate processors and won't do any smart scheduling. The conclusion from this is that there may be requests for the same resources and so result in some reduction in performance.

Other than that, there's the previously discussed problem if you have 2 HT CPUs; you won't be able to run that system on Windows 2000 Pro, since it will be counted as 4 processors.

 

[Goi]

I see...so all in all, Win XP is better for intel P4 HT CPUs? Not that I have one, I only have a P4 2.4B, but I was just curious...I much prefer Win2K to WinXP.

 

[spyordie007]

The difference is that supposedly WinXP will do a little better at process scheduling, so that threads minimise clashing for CPU resources. Windows 2000, seeing two processors, is going to really treat it as two separate processors and won't do any smart scheduling. The conclusion from this is that there may be requests for the same resources and so result in some reduction in performance.

The big performance problem under Windows 2000 is when you have multiple HT CPUs, for example you have Windows 2000 Server with dual P4 HT Zeons. Windows 2000 believes them to be 4 seperate physical CPUs.
CPU__A_____B
_____/\_____/\
____1_2___3_4
Windows 2000 than assigns tasks to the CPUs in order, it assigns the first thread to CPU "1" and the second to CPU "2" (beliving them to be seperate physical CPUs) so you have one CPU (A) working on both threads while the second CPU (B) sits idle. Windows XP/2003 knows that the system doesnt actually have 4 physical CPUs so it assigns the first thread to the first logical CPU (1) and the second thread to the first logical CPU on the second physical CPU (3), followed by the second logical on the first physical (2) and lastly the second logical on the second physical (4). This is where you will run into serious performance hits with HT enabled.

-Spy

 

[Goi]

OK. So the load balancing isn't optimal. Will MS issue a "fix" or "update" to address this problem though?

 

[bsobel]

Originally posted by: Goi
OK. So the load balancing isn't optimal. Will MS issue a "fix" or "update" to address this problem though?

No. HT is supported on XP and above (Win2k3 does support it).
Bill

 

[Nothinman]

You would need to make a lot of changes to the process scheduler, which would mean a major overhaul of the OS.

It would only require an overhaul of the OS if Microsoft is incompetent, changing the process scheduler should be a pretty small change and should also be transparent to everything else in the system.

 

[Budman]

Originally posted by: Nothinman

You would need to make a lot of changes to the process scheduler, which would mean a major overhaul of the OS.

It would only require an overhaul of the OS if Microsoft is incompetent, changing the process scheduler should be a pretty small change and should also be transparent to everything else in the system.

Yes but we are talking about Microsoft here. :disgust:


It could be done I am sure but they want to sell their shiny new XP OS.

 

[Goi]

I sure hope they do, but I guess its just wishful thinking on my part...*sigh*

 

[Nothinman]

It could be done I am sure but they want to sell their shiny new XP OS.

Of course, I'm not saying they will support HT more completely since they have XP now, but I'm saying it probably wouldn't be too difficult for them.