intel P4 3.06 (HT) Question
- Thread starter Anonymous
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BIOS setting. And doesn't it still only work on WinXP, or has Linux support been added?
Jackson technology? Must've missed that. And the 2k thing is news to me as well..
Originally, it only worked on WinXP, BUT it worked on XP Home, which doesn't support SMP. But if it now supports Linux or is OS-independent, more power to em.
It worked under any system that supports SMP. The two logical processors were recognised as physical ones under non-XP windows systems. Not sure what Linux does.
WinXP pro has SMP support for 2 processors physical processors. XP Home doesn't have SMP for physical processors but it does have it for 2 logical processors.
WinXP pro has SMP support for 2 processors physical processors. XP Home doesn't have SMP for physical processors but it does have it for 2 logical processors.
WinXp Home is a special case. Intel wants the ISVs to use the number of physical CPUs for licensing. Therefore, WinXP Home was designed to support SMP only for HTT. On the other hand, Win2k was not designed this way. So if you use dual HTT CPU with Win2k Pro, you'll see only two CPUs, not four.
EDIT: Saem you beat me
EDIT: Saem you beat me
Now I'm really confused. That just doesn't make any real sense... the two are almost identical! Care to provide a link to benches?3dcgi said:
I don't have any benchmarks, but it makes sense. Note that in real dual CPU systems, the OS always runs two threads at the same time, since you have two CPUs. However, in the case of HTT, you have only one CPU. When only one thread is running important work, you don't want to have two active threads, since the other thread will eat the CPU resource. This requires some OS support.
Furthermore, if you have two active threads which need synchronization, you'll want to avoid spin wait when using HTT. If spin wait is really required, you can insert a new instruction (PAUSE) to tell the CPU that the thread is doing no useful work. Fortunately, Intel claims the new instruction (PAUSE) has no meaning for any other x86 CPUs (actually PAUSE = REP NOP, which is an illegal instruction IIRC).
These are some examples of "optimizing" for HTT.
Furthermore, if you have two active threads which need synchronization, you'll want to avoid spin wait when using HTT. If spin wait is really required, you can insert a new instruction (PAUSE) to tell the CPU that the thread is doing no useful work. Fortunately, Intel claims the new instruction (PAUSE) has no meaning for any other x86 CPUs (actually PAUSE = REP NOP, which is an illegal instruction IIRC).
These are some examples of "optimizing" for HTT.
Sorry, this is false.pcchen said:WinXp Home is a special case. Intel wants the ISVs to use the number of physical CPUs for licensing. Therefore, WinXP Home was designed to support SMP only for HTT. On the other hand, Win2k was not designed this way. So if you use dual HTT CPU with Win2k Pro, you'll see only two CPUs, not four.
EDIT: Saem you beat me
If you use dual HTT Cpu's on win2kpro, you do infact see 4 cpu's. I have an example sitting in front of me.
Indeed, Win2k Pro only supports up to 2 CPUs. I somehow wonder if it can detect the amount of physical and logical CPUs. In that case, the restriction could be 2 physical CPUs.Saem said:
For linux, there is HT support starting from kernel 2.4.18 and onwards I believe, but the performance is quite bad from what I've heard. If you want fast HT performance under Linux, you should try a 2.5.x kernel.
I did try MDK 9.1 on my P4 3.06, but it didn't even recognise the 2 logical CPUs :? I couldn't really be bothered to try a new kernel, so I deleted Linux.
I don't have any benches to link, but pcchen's explanation is probably accurate. My information came from my brother who is an applications engineer for Intel and while I don't exactly remember our discussion on this I think it had to do with XP having knowledge of HT as pcchen explained.The Baron said:
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