To Hyperthread or not to Hyperthread

[Stormblade]

Hey all,

I just upgraded my system (See signature link of system specs). I have dual Xeons and currently I have hyperthreading enabled. The novelty of it has worn off and now I'm noticing pros and cons. Some programs and such run faster but I've noticed a speed decrease in some apps like Winrar and FSRaid which I find puzzling.

What do you all think about it? I've read a few reviews which also spoke of mixed results. One thing that's not clear to me is whether having it on cuts my CPU speed in half so that instead of running 2.4 Ghz I'm running like 1.2 but makes it like I have two of them instead.

 

[Duvie]

I have never heard of anything about a 50% penalty by having it on.....

I likley would not have it on much unless I was really running a lot of multitasking apps (which I do)

Also, I think the HT in these newer chips is a more revised HT and thus maybe there are some buggy issue with this in the xeon chips where HT by the way showed up first....It is likley it is not the exact same as the hT on the 3.06ghz desktop chip or the new p4c chips...

 

[sonoran]

Originally posted by: Stormblade
Hey all,
One thing that's not clear to me is whether having it on cuts my CPU speed in half so that instead of running 2.4 Ghz I'm running like 1.2 but makes it like I have two of them instead.

No, HyperThreading does not work anything like that. It makes use of additional circuits to try and prepare instructions from separate threads at the same time so that either can use the execution units when they become available. (They developed HyperThreading because they found that the execution units in a typical CPU were only doing useful work about 35% of the time!)

 

[Stormblade]

Thanks. I guess I'll leave it on for a bit and see. My system is way faster than my old one but I want to try and remove any bottlenecks that I can. Who knows, I may even try overclocking one of these days.

 

[Jeff7181]

Only in a select few benchmarks does HT hurt performance. And when it does hurt performance, I think it's only 1 or 2 % if I remember anandtech's benchmark results

 

[EXman]

I'm thinking about dumping my 2.4 (533) @ 3 Ghz and trying a 2.4 (800) w/ HT I think I can pop one of these in my BH7 and it will work.

I use my machine for some gaming an video editing

 

[Spicedaddy]

Originally posted by: EXman
I'm thinking about dumping my 2.4 (533) @ 3 Ghz and trying a 2.4 (800) w/ HT I think I can pop one of these in my BH7 and it will work.

I use my machine for some gaming an video editing

It'll work, but you probably won't overclock very high. 3GHz would mean 250FSB, I don't think the BH7 can get there...

 

[Duvie]

Originally posted by: Spicedaddy

Originally posted by: EXman
I'm thinking about dumping my 2.4 (533) @ 3 Ghz and trying a 2.4 (800) w/ HT I think I can pop one of these in my BH7 and it will work.

I use my machine for some gaming an video editing

It'll work, but you probably won't overclock very high. 3GHz would mean 250FSB, I don't think the BH7 can get there...

I have seen reports of ppl doing 230's....Also the albatron i845pe chipset board goes up to like 240, but I believe the best I have seen with a serious NB cooling mod was 219 range...

 

[EXman]

why 250FSB what is the multipiler? I know I can do at least 200mhz but 250 will take some work and new ram...


but the HT 2.4 800 will work on the BH7 correct.

 

[Duvie]

Originally posted by: EXman
why 250FSB what is the multipiler? I know I can do at least 200mhz but 250 will take some work and new ram...


but the HT 2.4 800 will work on the BH7 correct.

2.4c = 12 x200
2.6c = 13 x200
2.8c = 14 x200
3.0c = 15 x200
3.2c = 16 x200

Heck 230 is going to be work...got some pc3700 proven stuff, cause there isn't any 4:3 ratio I know of at that fsb...

 

[Spicedaddy]

230x12=2760
250x12=3 GHz

Of course the ram will also be a limit. That's why 865/875 are better... They can reach higher FSB, and run the ram slower than the CPU FSB. (and still get good bandwidth since it's dual channel)