Hyperthreading good or hyperthreading bad?

Posted on 2006-05-13
Last Modified: 2008-01-09
....or hyperthreading makes no difference?

I have a Sony PCV RS421V. It has HT.

I run processes that are CPU intensive - but i generally run them overnight when i want as much CPU power as possible devoted to one task.

I have heard contrasting opinions on whether HT is good or bad, or makes no difference for my type of use.

I would like to get rid of it if it will speed things up (and would need advice on how to do this).

Please advise.


Question by:davsay
    LVL 95

    Expert Comment

    by:Lee W, MVP
    Problem is you don't mention what your operating system is.

    HT is generally good, but Windows 2000 and earlier and Windows Me and earlier don't directly support it and it IS possible for HT to actually slow down the performance of the computer on systems running these operating systems.  If you run XP, XP is HT aware and the performance SHOULD be as good or better with it enabled then with it disabled.
    LVL 95

    Expert Comment

    by:Lee W, MVP
    You should be able to test things by disabling it and see how it goes.  Typically there is a setting in BIOS to allow it to be enabled or disabled.
    LVL 34

    Expert Comment

    The answer is: Definitely maybe.

    As leew said, it mainly depends on the OS. Modern versions of most OSes will generally indicate (somewhere in their docs) if HT is a help or hindrance.

    Author Comment

    Thanks for your replies.  I am running XP. I like the idea of a test - how would i get to the BIOS setting and change it? I'm not familiar with this.

    LVL 3

    Expert Comment

    At least 5 days I week, I use XP Pro computers that HAVE HT enabled, and that do NOT have HT enabled. Most of these PCs have very similar (if not the same) components, and all are P4s.

    For your general run of the mill tasks (word processing, surfing, etc) I really see no difference. But when you get into running larger programs, there is a difference. Hyper threading helps. If you don't know what it is, its basically a virtual processor. It can handle two threads at one time.

    If you are running a OS other than XP, I think it is generally not a good idea, because the support for it is much better in XP.
    LVL 87

    Accepted Solution

    It doesn't only depend on the OS, but also the applications. If you are using one application that can't use multiprocessors, you won't see much of a difference, but if you are using mor than one instance of that app, it is likely that one instance will use one processor and the other instance the other. In such a case you will see a positive difference.
    LVL 20

    Expert Comment

    LVL 2

    Assisted Solution

    To enter the BIOS on that particular computer, try pressing F2 as the computer is restarting. Maybe during the Sony splash screen, but before the Windows loading screen.
    LVL 2

    Expert Comment

    rindi has the correct answer for you.

    Some applications definately have issues with HT, but not many. I had a VMS emulation program that HT caused to run incredibly slow. Everything els on the machin ran faster with HT on. If the software companies don't tell you, the only option is to test yourself.

    For most applications it either doesn't make a difference, or else it make them faster. For the few that can't deal with HT, it will slow them down or make them crash.

    Assisted Solution

    If you are having issues with an app, that you are running unattended overnite, and you want to increase it's performance, and or determine if running it one way or another makes a differece, look at a service launcher called FireDaemon, it will allow you to assign the program to a CPU, since XP Thinks that they are two different cpus, by assigning it to the second one, leaving the primary kernel of the HT CPU unimpeded,   The program will think it is just running on one cpu, and not suffer the same effects if it was not designed for a multi-cpu environment, simulated or otherwise.

    thirty day trial,

    by utilizing something like this it will allow you to enjoy the full benefits of the system without hindering other programs that can take full advantage of HT.



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