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how good is hyper threading

By msdstc ยท 4 replies
Aug 18, 2005
  1. I have an intel P4 prescot, 3.0 ghz hyper threading technology, what exactly is hyperthreading and just how good is it?
  2. Blakhart

    Blakhart TS Rookie Posts: 353

    HT is an effort to keep the cpu busy, as in busy busy. Even though a cpu may show 100% useage, in actuality it might only be 30% _efficient_, instruction execution wise. This is because sometimes threads must wait on other threads, an os call, or i/o, to complete the function, thus leaving parts of the cpu idle. With HT the cpu is kept "more busy" by keeping the registers humming on two threads rather than on one single thread. Threads being basic cpu food. Well ok, threads are the actual parts of an application that gets processed by the cpu. Consider HT to be vestigial cpus rather than literal cpus, even though the os considers HT to be SMP. In a single cpu non HT system, only one thread can run at any given time. On a Symetric Multi Processor system, or HT enabled cpu, two or more threads can be run concurrently.

    The gist is that multithreaded apps can see a 5 to 30% boost in performance, and single threaded apps can see a benefit as the os can do something on the cpu at the same time as the app thread. This generaly means a smoother system. But not always; sometimes HT makes an app perform worse, as certain amounts of resource contention can occur in the cpu, creating delays not present in a non HT cpu. I'll take that risk.

    As you can see, dual core is the way of the future. HT is kinda being left behind, but is still worthy. The Prescott ver of the p4 has some slight enhancements that the earlier HT p4s don't have. Still, a p4 with HT enabled is better than a p4 without, no matter what the ver.

    The guts of it all can be found at arstechnica and other forums, as well as at Intel.
  3. luvr

    luvr TS Enthusiast Posts: 59

    HyperThreading is a single CPU pretending to be two CPUs. An Operating System (and any software) that supports Multi-Processor systems can, thus, do parallel processing, just as on a real multi-processor.

    Just as with real multi-processing, you will introduce a little overhead, because of the required synchronisation between the two CPU cores, so if you have a 3-GHz HyperThreading CPU, you won't all of a sudden run like two 3-GHz engines simultaneously - you will more likely see the performance of something like two 2.8-GHz or 2.6-GHz CPUs (depending on the quality of the multi-processor support in the Operating System), which is, of course, still great.

    Personally, I'm not interested in HyperThreading, and I disabled it in BIOS. But your mileage may vary; it can, of example, come in handy if you do lots of compute-intensive work, e.g., rendering or any encoding stuff.

    HyperThreading will be a great idea if you can make good use of it; otherwise, it won't generally make that much difference.
  4. msdstc

    msdstc TS Rookie Topic Starter Posts: 73

    alright thankyou very much for both your responses :)
  5. nein

    nein Banned Posts: 109

    HyperTreading is a hack originated from Distributed Processing, it is a work around for poorly designed, in-efficient processors.

    It isn't actually Multi-Threaded, just immitation of Multi-Threading, there is no multiple processors only fractional DIFFERENT PARTS of a single processor. The multi fractional instructions and data chunks are organized and hacked into single big chunks by programmers for normal conventional Symmetric Processing usage (one thing at a time) - because the poorly designed processor couldn't do so on its own.

    EG, it isn't a general CPU optimization, fully optimized only for use in specific controlled-conditions imposed by programmers.

    There are people actually dumb enough to buy this superior "FEATURE" (work around hack) invented by Intel. AMD don't have the "feature" exposed, AMD would first needed their processors designed to be broken and in-efficient in the exact same manner as Intel hardware did before they could even add the hardware "feature" in.

    Every newly design AMD processors with HyperThreading feature will also had to have been first similarly broken in the exact same way before adding the "feature".

    Summation: HyperThreading is a work around hack for poorly designed processors, sold to ignorant fools as a hardware feature of superior technology.
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