Core I7, shoudl hyperthreading be disable ?

bigdogchris said:
I'm under the impression that HT was badass when there were only single core CPU's, hell I had a HT p4 and it was wicked. With 2 or more cores I don't really see a point in it.
Click to expand...

Well, you're partially right there.
Single threaded apps (incl most games, and most apps for that matter) won't show any real diff.
If you're a Maya or PShop user, then absolutely, there's real (25%-40%), tangible improvement.

But, most stuff today shows little if any benefit and some games show loss of performance with HT. See where you fall.
 
Zero82z said:
Anyone who runs a lot of VMs and does a lot of multitasking will benefit a lot from HT. I have two VMs running for Folding@Home and I could definitely use the extra threads that an i7 would provide me with. When I'm running a lot of programs my CPU definitely gets bogged down, and it's running a healthy 1GHz overclock.
Click to expand...

Not to threadjack but I'm not understanding this right...

You run 2VM's to fold, wouldn't it be the same if you were able to allocate your 'whole' processor to just one instance of folding@home?

The only think I can think of is if folding only supports 1-2 threads... just a guess.

Again, sorry to thread jack but I'm perplexed.
 
Dan, I would add to your comments regarding the only need to disable HT would be if you are a benchmarking whore.

In my case, and many others on this board, HT was limiting my absolute max overclock.
Just too much heat gets generated on an I7 by turning on HT to justify me having it on.
As we ARE enthusiasts, and this IS and Overclocking community, I don't think we can discount the absolute need to wring the living electrons out of these chunks of Si Intel deals. I can hear my chip scream louder at 4.2 than at 4.0, and I find that comforting at night.
 
MassiveOverkill said:
Just realized you don't have an i7 either, and I'm done talking to you as well ;)
Click to expand...

Ignorant much? :eek:

Just because you own something doesn't mean you understand how it works. You probably own a car too... care to explain how the torque converter in an automatic transmission works?

The thermal management in ANY modern cpu will prevent it from damaging itself. We all understand that temperatures are generally higher with HT enabled, but it's a normally functioning part of the processor. Overclocking is not. Disabling HT is a workaround that may work for some people, but that doesn't mean it's at fault for the chip running too hot.

I guess I don't own an i7 yet either so you can't take me seriously.:rolleyes: Guess I'll have to come back in a few days when it shows up and I become enlightened.
 
Morazl said:
Not to threadjack but I'm not understanding this right...

You run 2VM's to fold, wouldn't it be the same if you were able to allocate your 'whole' processor to just one instance of folding@home?

The only think I can think of is if folding only supports 1-2 threads... just a guess.

Again, sorry to thread jack but I'm perplexed.
Click to expand...

Free VM software only allows two-core VMs, so I have to run two in order to take advantage of my entire processor. Ideally I'd run a single VM across four cores, but I'd need to buy commercial software to do that and I don't have any real need or desire to spend money on that.
 
MassiveOverkill said:
Just realized you don't have an i7 either, and I'm done talking to you as well ;)
Click to expand...

You're really quite ignorant. If your system is unstable immediately after OCing it's due to you not using the right bios settings / you've pushed your chip too far that it can handle. Heat diminishes the lifespan of anything, but it doesn't cause BSOD's in new CPUs in mere minutes/seconds, because as noted above by other people and via every technical legitimate website I7's throttle before heat becomes a killer.

No I don't own an I7 and never will but I do know how to read properly.
 
Does anybody know if hyperthreading has a negative or positive impact on metro 2033? I thought i read that dx11 games could benefit from hyperthreading.
 
tyguy said:
Does anybody know if hyperthreading has a negative or positive impact on metro 2033? I thought i read that dx11 games could benefit from hyperthreading.
Click to expand...

ANY program "can" benefit from hyperthreading if the program itself supports more threads than your processor has cores.

How many threads does metro 2033 support?
 
cyclone3d said:
ANY program "can" benefit from hyperthreading if the program itself supports more threads than your processor has cores.

How many threads does metro 2033 support?
Click to expand...
I have no idea. I'm asking because some older games seem to run a little better with hyper threading disabled. Although the link earlier on in the thread was old and used windows vista. Maybe hyper threading in games isn't a detriment in 7 like in vista. There is also this thread in regards to gta 4 which benefits greatly from quad cores but apparently has slower performance with hyper threading.

http://hardforum.com/showthread.php?t=1511702
 
Has anyone done any gaming performance tests comparing core parking on/off?
 
cyclone3d said:
Look into disabling "core parking" in Windows. Apparently it helps in certain audio software and some games on systems that have more than 2 physical cores available.
Click to expand...

What's the difference between core parking and SMT parking? Some say they're the same feature. If so, disabling it should actually lower performance because the scheduler won't distinguish physical cores from logical (HT) cores. You'd have two threads executed on one core when there is another physical core available.

And yes, I actually own an i7. Not that it matters.
 
Running fluid simulations on an i7, HT didn't help at all, infact it probably slightly hurt performance. I specified it to run on 8 threads, and it did, but it struggled more to maintain 100% CPU usage compared to running 4 cores without HT, where it stays at 100% pretty solidly.
 
Tudz said:
Running fluid simulations on an i7, HT didn't help at all, infact it probably slightly hurt performance. I specified it to run on 8 threads, and it did, but it struggled more to maintain 100% CPU usage compared to running 4 cores without HT, where it stays at 100% pretty solidly.
Click to expand...
Then that's a failing of the software, not HT. Failure to consistently reach 100% load means the program is having trouble properly dividing the workload between all 8 threads.
 
Tudz said:
Running fluid simulations on an i7, HT didn't help at all, infact it probably slightly hurt performance. I specified it to run on 8 threads, and it did, but it struggled more to maintain 100% CPU usage compared to running 4 cores without HT, where it stays at 100% pretty solidly.
Click to expand...
Software will not be 100% efficient for just *any* number of threads. I am also imagining dual W5680s with HT on == 24 cores/threads may be a struggle even for most current multi-threaded bench mark software. Of course there is very little overhead with those codes as they don't really do a lot, so maybe. Fluid simulations code could have coordinate conversion, convergent test, and any number of other operations as a part of every iteration ... and may not have been totally optimized as it could be.

I have some software that starts losing efficiency at 4 to 6 threads, but I can run multiple instances (for different variations of the same problem) and then get in >>90% CPU utilization.
 
Psi* said:
Software will not be 100% efficient for just *any* number of threads. I am also imagining dual W5680s with HT on == 24 cores/threads may be a struggle even for most current multi-threaded bench mark software. Of course there is very little overhead with those codes as they don't really do a lot, so maybe. Fluid simulations code could have coordinate conversion, convergent test, and any number of other operations as a part of every iteration ... and may not have been totally optimized as it could be.

I have some software that starts losing efficiency at 4 to 6 threads, but I can run multiple instances (for different variations of the same problem) and then get in >>90% CPU utilization.
Click to expand...

When I say "struggled to maintain 100%" I mean it was running at about 95% most the time when using HT, compared to 98-100% when simply using 4 cores without HT, overall this resulted in an increase in time per iteration when using HT. The software is pretty well designed for parallel processing, as it is designed to scale well when being used on clusters of 100s of processors. Though I guess each core can still only do so much, and its not doing any more when HT is active, just splitting it more times.

I didn't mean to say "HT sucks" with my post ;) simply that on my number-crunching machine I've disabled it because everything runs noticably slower with it on.
 
my friend has a 860 and disabling ht gives him a huge gain in superpi. this is under phase at 4.8ghz.

before disabling ht superpi was slower than the q9650 at 4.7ghz.
 
I was having pretty slow fps in Age of Conan this weekend (just signed up).

Running an i7-860 @ 4.0ghz on water. GTX 470 on air. The client is supposed to be multicore aware, and it looked like it was hitting a 2nd thread for maybe 10% or so. One core was at 100% with a 2nd just barely in use. Couldn't figure it out so I thought of disabling hyperthreading. Major improvement.

Easily a 30% to 50% increase in fps. From what I can gather, the client was trying to use one of the virtual hyperthreads instead of actually using a logical core, which was interrupting the thread, causing slower fps than it should have been.

Hyperthreading still seems to be only good for looking at 8 threads in benchmarks, and increasing cpu temps.
 
cyclone3d said:
ANY program "can" benefit from hyperthreading if the program itself supports more threads than your processor has cores.

How many threads does metro 2033 support?
Click to expand...

That's very very wrong.

I was under the same impression not long ago because all the tech sites always keep talking about multi-threaded application able to take advantage of HT. However, as I just recently found out, it really depend on the natural of the program and how it's written. The test code I write for Matlab and MAthmatica to test their performance runs between 20-40 threads, yet the speed drops noticeably once I enable HT, it turns out they are using only physical core for their low level operation, and enable HT prevent them from max out usage of any/all physical core, and in turn lower the speed.
 
sskk said:
That's very very wrong.

I was under the same impression not long ago because all the tech sites always keep talking about multi-threaded application able to take advantage of HT. However, as I just recently found out, it really depend on the natural of the program and how it's written. The test code I write for Matlab and MAthmatica to test their performance runs between 20-40 threads, yet the speed drops noticeably once I enable HT, it turns out they are using only physical core for their low level operation, and enable HT prevent them from max out usage of any/all physical core, and in turn lower the speed.
Click to expand...

Why 20-40 threads? The i7 only has support to run 8 threads at once...

And IF it is actually only using physical cores and not the HT cores.... then matlab and mathmatica have sucky threading support... sounds like they only really support 4 threads... in which case, HT won't help when running it on an i7.

Mathmatica only started supporting more than one thread when version 5 came out if I remember correctly.

And I won't even begin to say what I think of MATLAB. I had a college engineering course where we were forced to use MATLAB.... worst program ever... half the stuff didn't work like it said it did according to the documentation.

Maybe I should have said... any program with half decent threading can benefit from HT if it properly supports more threads then you have CPU cores.
 
cyclone3d said:
Why 20-40 threads? The i7 only has support to run 8 threads at once...

And IF it is actually only using physical cores and not the HT cores.... then matlab and mathmatica have sucky threading support... sounds like they only really support 4 threads... in which case, HT won't help when running it on an i7.

Mathmatica only started supporting more than one thread when version 5 came out if I remember correctly.

And I won't even begin to say what I think of MATLAB. I had a college engineering course where we were forced to use MATLAB.... worst program ever... half the stuff didn't work like it said it did according to the documentation.

Maybe I should have said... any program with half decent threading can benefit from HT if it properly supports more threads then you have CPU cores.
Click to expand...

I've used MATLAB quite a bit in my course, I never had any problems with it not doing what the documentation said it could do. But that said I've never explored its threading capabilities.

Other programs I've used that scale almost 100% when used on 2, 4, 8, or up to 128 cores still run worse with HT enabled. I've run fluid sims that scaled perfectly when running distributed across a cluster. Sims run in that same program run worse with HT enabled.

Perhaps it has to do with the way it uses the cores? Physics simulation programs tend to use the CPU to 100% regardless of the number of threads you run, so the only way HT could add any extra performance is if it magically let the CPU use more than 100%.
 
After skimming thru this thread (I too now own an i7 woot) the consensus I kept thinking of is there's a good use to those multiple bios save slots once you've discovered your system's strengths. I guess it comes down to how much more of an OC you can pull off with HT off. Right now I'm still testing with P95 @ 3.75Ghz and my temps are 80C. I'm thinking I can probably hit that magic 4Ghz with HT off and the same temps. Dunno if I would 'notice' in RL apps and games the 250Mhz difference but I already see a difference in my desktop playing and a brief WoW session (it is a CPU hog after all) from my former 3.2Ghz C2Q desktop.
 
aintz said:
my friend has a 860 and disabling ht gives him a huge gain in superpi. this is under phase at 4.8ghz.

before disabling ht superpi was slower than the q9650 at 4.7ghz.
Click to expand...

I noticed that. With HT on at 4 GHz I can complete a 25K problem size pass of Linpack in roughly 193 or so seconds. With HT off it's somewhere around 170 seconds.

Some workloads just don't scale well with HT. Many do though, and that's why it's beneficial to have it on IMO.

RiPpLeeFFecT said:
I was having pretty slow fps in Age of Conan this weekend (just signed up).
Click to expand...

Are you using Windows 7? Vista and XP didn't have SMT parking. A physical core and one logical thread were treated as two separate processors, and so if you had 3 physical cores available, the scheduler would assign threads to an HT thread even though a physical core was available.

In those cases, it's almost always beneficial to disable HT on the i7. (HT was an improvement for the Pentium 4, and it did not have these issues because it was limited to two threads, not 8.)
 
wow.. a debate about hyperthreading on hardforums?

Hyperthreading is a gimic, and should always be disabled.
 
Gadfly said:
wow.. a debate about hyperthreading on hardforums?

Hyperthreading is a gimic, and should always be disabled.
Click to expand...

<buzzer> Wrong answer! It is a very real technology, with very real benefits.
 
rflcptr said:
<buzzer> Wrong answer! It is a very real technology, with very real benefits.
Click to expand...

I beg to differ. I have run Hyperthreading since it's release, on every form of on intel processor it has shipped on (mainly on servers), and it has never made an impact on real world performance. A few benchmarks, sure, depending on which one you run, but in real life number crunching, especially in high I/O enviorments, it just does not help, in fact most of the time it makes things worse.

AND no matter what marketing material you may read, the real bottom line is under current architexture each processor can still only process one thread at a time, no matter how many hyper threads you are running, they are still waiting for processor time, they just wait in a diffrent line.

It is a gimic, Hyper threading's overhead equals or outweighs it's benefits in every real world test you can throw at it, but one, and it drives your thermal load up. So when is hyperthreading a good thing? On high density virtual hosts. If you are running a high density virtual host, hyperthreading works very well, especially true when you start to get into the 32+ core range.

High I/O, multi-threaded loads, such as Databases, webservers, etc. is the worst case for hyperthreading. Gaming.. don't think it will make a bit of diffrence other than make your processor run hotter. For an overclocker, you will be much better served to disable hyperthreading and run a higher overclock. 25mhz of clock speed will by far out perform anything that hyperthreading would give you.
 
Last edited:
ShuttleLuv said:
LOL maybe in 2003 it was, but it can show very real, beneficial gains nowadays.
Click to expand...

no, in 2003 p4 3.0c I bought was much better with HT on. Not to say the HT was better, it was mostly because it has one core, so multi tasking was clearly better with it's on, with quad core now, any benefit is not noticeable at all, while my matlab code was clearly slower.
 
In SC2, with all the CPU settings maxed out I was getting around 30 fps. I then disabled HT and my fps shot up to 50+. Also while watching videos on YouTube full screen the video would stutter/freeze for a second every 10-15 seconds, with the audio still going. This problem doesn't exist when I turn HT off. So for now I'm leaving it off. CPU is not overclocked.
 
Gadfly said:
wow.. a debate about hyperthreading on hardforums?

Hyperthreading is a gimic, and should always be disabled.
Click to expand...

I max out all 8 threads on my i7 860 at work every single day that I sit at the computer. It does provide real benefits over the same chip with 4 threads only. However for those who never do stuff that uses 4 threads at 100 % cpu (I would max out a 16/20 threaded cpu easily) it probably will be better to leave it off.
 
sskk said:
no, in 2003 p4 3.0c I bought was much better with HT on. Not to say the HT was better, it was mostly because it has one core, so multi tasking was clearly better with it's on, with quad core now, any benefit is not noticeable at all, while my matlab code was clearly slower.
Click to expand...

Can matlab use more than 4 threads at a time at 100% CPU?
 
drescherjm said:
I max out all 8 threads on my i7 860 at work every single day that I sit at the computer. It does provide real benefits over the same chip with 4 threads only. However for those who never do stuff that uses 4 threads at 100 % cpu (I would max out a 16/20 threaded cpu easily) it probably will be better to leave it off.
Click to expand...

I use programs that use 8 threads at 100% no worries and still HT slows them down and they're better off running 4 threads on 4 cores. Almost any good physics solver running through MPI will use 4 threads maxed out for hours on end.
 
i use my i7-920 at 4.51GHz with HT on 24/7.my last one i ran it with HT off because it needed so much vcore.but i got lucky with this one because at 4515 i HT on i only need 1.34v to be stable in win7 x64.
i hated having to not use HT on my last one because i mean thats why i got it to have 8t running:D
 
You must log in or register to reply here.
Back
Top