Hyperthreading Questions

timwhit

Hairy Aussie
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Jan 23, 2002
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My work computer is an old Dell Optiplex GX270 with a P4 3.2GHz CPU.

Needless to say, whoever set this up was not very bright. Someone added a second hard disk at some point and they never enabled the controller in the BIOS, the hard disk showed up in Windows, but it was running in PIO mode, probably for the last 4 years or so.

Anyways, when I was fixing that I noticed that hyperthreading was disabled in the BIOS, so I thought, why not enable this and maybe I will get a little performance boost. When the system restarted I got a message that Windows XP had installed the new hardware and I need to restart. I restarted and everything came up. I can now see two logical processors in Sysinternals Process Explorer. I haven't noticed a difference in performance yet. Either way, is it really working or does the OS ideally need to be reinstalled for this to actually work? Or am I good to go? If the OS needs to reinstalled, would an inplace install work?

More general questions:
Is there any real performance boost with HT enabled?

Does an application need to be SMP aware to take advantage of HT? The main applications that I run are BEA Weblogic Workshop (based on Eclipse), BEA Weblogic Server, Photoshop, Dreamweaver, and MS Office XP.
 

sechs

Storage? I am Storage!
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As long as the multiprocessor HAL is installed and working, then you should be fine. That there are two processors in the task manager is a good sign.

If you keep in mind that the number of actual processors in your system has not changed, the gain from hyperthreading is not terribly good. I've never felt a meaningful gain from it, but also keep in mind that I use a dual processor system at home.
 

timwhit

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As long as the multiprocessor HAL is installed and working, then you should be fine. That there are two processors in the task manager is a good sign.

If you keep in mind that the number of actual processors in your system has not changed, the gain from hyperthreading is not terribly good. I've never felt a meaningful gain from it, but also keep in mind that I use a dual processor system at home.

That's good to hear.

Any gain I can get will be appreciated even if it is only 5-10%. After using the system all afternoon it does feel a little bit faster, which is nice. What would be really nice is a new system and 2 LCDs, instead of the 2 ancient CRTs I'm using now. After 8 hours of using that computer my eyes are killing me.
 

Handruin

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I've always looked at hyperthreading as a way to keep the machine responsive in the event a process consumes 100% of the CPU time. Having that extra thread (or logical division of a CPU) might allow your system to feel slightly more responsive during intense times because it will allow other threads to get some time on the CPU. For example, updating GUI components, some other running task, etc.
 

timwhit

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Chicago, IL
My systems is at 100% CPU much of the time when doing application development. The tools just aren't very efficient. It seems to be helping.
 
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