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Old 08-14-2011, 07:57 AM   #16
cascade9
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Quote:
Originally Posted by johnsfine View Post
I expect it is hard to do a meaningful performance comparison. The results would depend heavily on details of configuration and workload.
Agreed 100%.

Finding decent benchmarks in general can be hard enough. Far to many 'benchmarking' sites just use a the framerate on 3D games, and maybe a few artifical benchmarks.

I tried looking for the article I wanted, I simply couldnt find it again.

Anyway, this is farily typcial of hyperthreading on/off benchmarking-

http://www.bit-tech.net/hardware/cpu...-cpu-review/10

Some things run slightly faster, some things slightly slower.

BTW, more for johnsfines interest than the OPs, I also found this-

http://www.ibm.com/developerworks/linux/library/l-htl/

Obsolete but interesting.
 
Old 08-15-2011, 02:04 AM   #17
nec207
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Quote:
Originally Posted by jefro View Post
In all of this, it basically makes no difference. Some programs will benefit from the cores while others will not. Some work better on hyperthreads and others go slower.

In tests you sometimes see dual core system stomp quad cores just because the clock speed is higher in the dual core.
From my understanding the OS or program has to be program to work with hyperthreading for a speed increase.

That say the game Doom it is not program for hyperthreading so no increase in speed.Now that say in 2 years from now there is new Doom game called Doom 8 now you got a speed increase do to that game was program for hyper threading.
 
Old 08-15-2011, 06:24 AM   #18
cascade9
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Quote:
Originally Posted by nec207 View Post
From my understanding the OS or program has to be program to work with hyperthreading for a speed increase.
Not that simple.

If the program you are running is multi-threaded, hyperthreading should give you some advantage. That isnt always the case, lots of programs that are multi-threaded are slower with HT turned on than with HT turned off.

Some of those programs are getting much smaller 'penalties' with 'sandy bridge' CPUs and HT turned on than with earlier HT CPUs. From what I'm seeing around the net, that is mainly due to hardware changes wih the newer 'sandy bridge' CPUs (mainly due to a faster L3 cache than the earlier CPUs). The actual software hasnt been updated at all.

Last edited by cascade9; 08-17-2011 at 06:39 PM.
 
Old 08-15-2011, 05:37 PM   #19
nec207
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Quote:
Originally Posted by cascade9 View Post
Not that simple.

If the program you are running is multi-threaded, hyperthreading should give you some advantage. That isnt always the case, lots of programs that are multi-threaded are slower with HT turned on than with HT turned off.

Some of those progrmas are gettign much smaller 'penalties' with 'sandy bridge' CPUs and HT turned on than with earlier HT CPUs. From what I'm seeing around the net, that is mainly due to hardware changes wih the newer 'sandy bridge' CPUs (mainly due to a faster L3 cache than the earlier CPUs). The actual software hasnt been updated at all.
The software is not program to work with new hyperthreading or sandy bridge CPU's ?
 
Old 08-15-2011, 06:47 PM   #20
TobiSGD
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Quote:
Originally Posted by nec207 View Post
The software is not program to work with new hyperthreading or sandy bridge CPU's ?
Almost no software is programmed for a specific CPU (at least in the desktop and server market, this may differ in high performance computing or with embedded devices). Of course the software will run on Sandybridge, and it will also work with Hyperthreading, but it may be slower than with Hyperthreading disabled.
 
  


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