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Old 10-25-2006, 09:47 AM   #1
avi85
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Default What are the disadvantages of turning off hyper-threading?

I was wondering what the disadvantages of turning off hyper-threading are (I saw the option in the BIOS)? Are there any advantages? this is in a 3.0GHz Prescott socket 478.
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Old 10-25-2006, 10:15 AM   #2
BrownTown
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Default What are the disadvantages of turning off hyper-threading?

Disadvantages would be lower multithread performance in some apps. Advantges would be slightly better performance in some apps. Its mostly just a cr@pshoot whether or not it will help what you are doing, so unless you have a specific program in mind it doesn't I would just leave it on.
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Old 10-25-2006, 02:55 PM   #3
imported_goku
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Default What are the disadvantages of turning off hyper-threading?

Just keep it enabled, it will prevent one buggy application from taking all the CPU cycles away from the system. It definately has a performance improvement when an application is coded to take advantage of it. The difference between HT and non HT is like the difference between a P4 3.5GHZ HT off and a P4 3.8GHz HT off. (300mhz difference)
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Old 10-25-2006, 03:25 PM   #4
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Default What are the disadvantages of turning off hyper-threading?

Hyperthreading genraly gives about a 15-20% performance increase in SMP aware programs, and helps with multi-tasking. Other than a few games, games are not SMP aware, and don't see a benifit from hyperthreading, unless you have some CPU intensive programs running in the background. There are also some odd programs here and there that perform better with HT turned off, but not usualy by a large amount.
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Old 10-25-2006, 04:25 PM   #5
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Default What are the disadvantages of turning off hyper-threading?

Quote:
Originally posted by: goku
Just keep it enabled, it will prevent one buggy application from taking all the CPU cycles away from the system. It definately has a performance improvement when an application is coded to take advantage of it. The difference between HT and non HT is like the difference between a P4 3.5GHZ HT off and a P4 3.8GHz HT off. (300mhz difference)

3.06 w/HT outperforms 3.6ghz w/o HT

Watch THG Video 5
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Old 10-25-2006, 07:25 PM   #6
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Default What are the disadvantages of turning off hyper-threading?

^actuall results may vary^
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Old 10-25-2006, 07:39 PM   #7
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Default What are the disadvantages of turning off hyper-threading?

More sluggish multitasking and SMP-programs runs slower. There is zero reason to turn HT off anyway; it is easily the best feature of the netburst architecture.
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Old 10-25-2006, 07:59 PM   #8
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Default What are the disadvantages of turning off hyper-threading?

slower SMP performance, but not by much. i'd just leave it on (you go from a 533FSB to a 800FSB).
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Old 10-25-2006, 08:07 PM   #9
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Default What are the disadvantages of turning off hyper-threading?

Quote:
Originally posted by: secretanchitman
slower SMP performance, but not by much. i'd just leave it on (you go from a 533FSB to a 800FSB).
??? Hyperthreading has nothing to do with the front side bus..
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Old 10-25-2006, 11:13 PM   #10
imported_goku
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Default What are the disadvantages of turning off hyper-threading?

Quote:
Originally posted by: RussianSensation
Quote:
Originally posted by: goku
Just keep it enabled, it will prevent one buggy application from taking all the CPU cycles away from the system. It definately has a performance improvement when an application is coded to take advantage of it. The difference between HT and non HT is like the difference between a P4 3.5GHZ HT off and a P4 3.8GHz HT off. (300mhz difference)

3.06 w/HT outperforms 3.6ghz w/o HT

Watch THG Video 5
Hmm, well while that IS an interesting video, what needs to be compared though is single application, multithreaded performance.

I came up with the 300mhz figure because I overclocked my processor to 3.8ghz one time and disabled HT, ran sisoft sandra then I compared the scores of my 3.5GHZ overclock with HT on and the scores were about the same.
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Old 10-26-2006, 02:06 AM   #11
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Default What are the disadvantages of turning off hyper-threading?

Disabling HT would be like having a Celeron or Athlon XP... completely neutering multitasking and video performance. Well, Athlon XP still couldn't compete due to lack of SSE2 +.
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