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Pentium 4 Hyperthreading

Anyone with a Pentium 4 3.06GHZ+ care to comment on how much of a performance boost they see?

Has anyone made use of this technology?  or is this the operating systems job? or the compilers job?  If it is the compilers job I wonder if the .NET CLR makes use of it or any other compilers for that matter?

Isn't this just a trick to make it appear that applications are processing faster?

mov ax, es:[di]
Thursday, May 15, 2003

I've got the 3.06, and it's fast like a greased monkey. I find that I have no delays at all while running many programs, though that may be just because the processor is so freaking fast.

I'm satisfied, but I didn't pay for it, per se. :-)

Tim Sullivan
Thursday, May 15, 2003

I've read 0-20% performance increase with hyperthreading, depending on the application(s) you're running. I've also heard that in a few rare circumstances, you actually lose performance (although I don't know what the key factor was there).

Brad Wilson (
Thursday, May 15, 2003

The OS (XP) takes care of it for you - you don't have to do anything.  Each CPU looks like two to the OS - the task manager shows two distinct CPUs for each actual chip.  A friend of mine has a dual hyperthreaded Xeon so his task manager says he has four CPUs.  He's had the thing a month and he still isn't tired of telling me how fast it is.

Mitch & Murray (from downtown)
Thursday, May 15, 2003

The last time I looked, Intel's compiler is compatible with Microsoft's; can compile faster code; is also better at generating code which adapts to or is suited for whichever Intel CPU.

Christopher Wells
Friday, May 16, 2003

Hyperthreading can boost performance by quite a bit in some cases.

Here is two articles on this:

Intel's Pentium Performance Hangs on a Hyper-Thread

Hyper-Threading On The Desktop

Albert D. Kallal
Edmonton, Alberta Canada

Albert D. Kallal
Friday, May 16, 2003

This must be the shortest write-up produced by Albert! :))
Albert, please don't get upset; I respect you a lot and enjoy your thoughts!

Friday, May 16, 2003

Where hyperthreading slows the application down is in heavy mathematics computation. While the hyperthreaded CPU appears to be two virtual processors, there is still only one FPU - and they have to share it.

I recently began a new position where we build large linux-based clusters, for labs and universities. The very FIRST bit of training I recieved - ALWAYS turn of hyperthreading in the BIOS, and let the customer do application profiling to decide if they see a performance increase or decrease. More often than not, with what they do, there will be a performance decrease with hyperthreading turned on.

Wayne Earl
Friday, May 16, 2003

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