Do most of you who've OC'd your i7's disable HT?

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Brahmzy

Supreme [H]ardness
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I'm thinking of trying for a 3.8 - 4.0 GHz OC on a 920 with good air. Does disabling HT help with the OC itself or just help keep the heat more under control/both?
 
Apparently the temperatures drop by upto 15c
I haven't tried it to be honest.
 
Rossi~ said:
Apparently the temperatures drop by upto 15c
I haven't tried it to be honest.
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Really? Isn't HT pretty much virtual? Are areas of the CPU being used with HT turned on that aren't used with it turned off? Why would it generate so much extra heat?
 
Really? Isn't HT pretty much virtual? Are areas of the CPU being used with HT turned on that aren't used with it turned off? Why would it generate so much extra heat?
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The extra processing the cpu is doing when HT is enabled will generate more heat and use more power although 15C sounds a bit much.
 
HT will give you a maximum of 20% speed increase over not using HT.

If it is dropping the temps 15C when overclocked... then people need to either get CPU coolers that actually work or learn how to use good heat transfer compound and/or mount their CPU cooler properly.
 
i7 920: HT on,VCore 1.35V
watercooled
BClk 185
3.8 GHz
idle 28C, load 45C......as sensed by the X58 onboard LED on the evga board.
e-leet software reads about 10C higher across the board, CPUID Hardware monitor reads consistant with the onboard LED......and the CPUID Hardware monitor has been pretty accurate on my previous MBs.
 
magoo said:
i7 920: HT on,VCore 1.35V
watercooled
BClk 185
3.8 GHz
idle 28C, load 45C......as sensed by the X58 onboard LED on the evga board.
e-leet software reads about 10C higher across the board, CPUID Hardware monitor reads consistant with the onboard LED......and the CPUID Hardware monitor has been pretty accurate on my previous MBs.
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Does it run cooler with HT off?
 
I've never disabled Hyperthreading on the Core i7 for overclocking.
 
yes, ht is disabled. runs cooler and overclocks higher in my experience. 20% speed increase with ht enabled? so if i enable ht will i be running at 4980mhz? well anyway i havent noticed any difference in performance between enabled/disabled.
 
Yes, ht is disabled. runs cooler and overclocks higher in my experience. 20% speed increase with ht enabled?
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That should be average performance increase and not speed.

so if i enable ht will i be running at 4980mhz?
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No, most likely (just as you said) you will not get as high of clocks with it on.

well anyway i havent noticed any difference in performance between enabled/disabled.
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Probably because you are not running applications that make use of 8 cores. There are not many that will...
 
Try this guys, run your 920's at 19x multiplier + whatever bclk needed to run your current speeds.

Doing this, i notice i can drop my vcore from .05 to .1 less than running it on 20x multiplier.

Im currently running 19x210 = 4ghz @ 1.275 vcore. This is with HT on.

Using 20x200 it takes me 1.375 vcore to remain stable.

I guess that this will work with all other 920's unless I just have a weird cpu here.

Forceman said:
Yeah, kind of defeats the purpose of going with the i7 if you do.
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Yeah agreed. I dont like it when reviewers do the same thing as well.
 
So you're saying there's no benefit going to an i7 over say an older 45nm quad other than HT? (Asking a serious question here.)
 
Brahmzy said:
So you're saying there's no benefit going to an i7 over say an older 45nm quad other than HT? (Asking a serious question here.)
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Youre running at 4.4 ghz, my gf's computer i have running at 4.5 dual core, and seriously cant tell a difference on desktop between E8500 @ 4.5ghz and I7 920 @ 4ghz.
 
Never turn it off, only when i hit the maxrecommended for i7 1,55Vcore i will turn it off to get higher but if the performance is worse then it is back down again as some have seen a difference to the worse by turning it off.
 
Brahmzy said:
So you're saying there's no benefit going to an i7 over say an older 45nm quad other than HT? (Asking a serious question here.)
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Depends on how much the application makes use of the integrated memory controller and cache really.
 
Geez, I'm really not seeing a real benefit to i7 over...say...a Q9550. I mean, take rendering for example, which I do a bit of. I JUST bought the new version of the software I use which now allows for 4 cores to be used (no more than 4). Now I'm thinking quad-core. So, it seems most folks can hit around 4.0GHz on air with a Q9550 where most folks are around 3.8-3.9GHz on air with i7 (a few have hit 4.0GHz, but it's usually around 3.8 or so)... So what am I better off with? I mean if I'm rendering a scene that takes 6 hours... will an slightly lower clocked i7 give me an edge over the Yorkie?
The benfits with i7 just aren't jumping out at me over the Yorkie's. Enlighten me please...

Also, does is the i7 940 a better overclocker than the 920?
 
Also, does is the i7 940 a better overclocker than the 920?
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I don't know about the encoding improvement but based on what I have read extensively on xtremesystems, the 920 and 940 oc about the same.
 
drescherjm said:
That should be average performance increase and not speed.



No, most likely (just as you said) you will not get as high of clocks with it on.



Probably because you are not running applications that make use of 8 cores. There are not many that will...
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yes i realize this, it was just a response to the guy who claimed 20% speed increase with ht, and to the guys who claim that they would be able to tell if ht was enabled or disabled while running apps in windows, or it would actually make any real world difference today. this is hardocp. my machine runs faster with ht disabled. there you go. when i am running telemetry for nasa, i will enable ht.
 
vanilla_guerilla said:
yes, ht is disabled. runs cooler and overclocks higher in my experience. 20% speed increase with ht enabled? so if i enable ht will i be running at 4980mhz? well anyway i havent noticed any difference in performance between enabled/disabled.
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Uh no, you don't get higher clock speeds with HT enabled. You should know better.


See the thing is the Core i7 has a slower front-end instruction decoder than the core 2 duo thought its back-end is a lot faster to support hyper threading. I've been able to squeeze out very nearly 4 instructions per clock cycle on a single core using two threads (5 if you count address generation micro-ops as an instruction) but only 2.5 on a single thread (on the core 2 duo it was at 3 IPC consistantly). Its because the instruction decoder can only handle 16 bytes per clock and 3 instructions--and at least two of those instructions must be simple u-ops. Not sure if the instruction decoder has to stall when the complex instruction straddles the 16 byte boundry.



The only reason I can think anyone would upgrade from a quad core to an i7 and disable hyper-threading is to flex their nuts on the interwebnet.
 
old skool said:
Uh no, you don't get higher clock speeds with HT enabled. You should know better.


See the thing is the Core i7 has a slower front-end instruction decoder than the core 2 duo thought its back-end is a lot faster to support hyper threading. I've been able to squeeze out very nearly 4 instructions per clock cycle on a single core using two threads (5 if you count address generation micro-ops as an instruction) but only 2.5 on a single thread (on the core 2 duo it was at 3 IPC consistantly). Its because the instruction decoder can only handle 16 bytes per clock and 3 instructions--and at least two of those instructions must be simple u-ops. Not sure if the instruction decoder has to stall when the complex instruction straddles the 16 byte boundry.





The only reason I can think anyone would upgrade from a quad core to an i7 and disable hyper-threading is to flex their nuts on the interwebnet.
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You summed that up perfectly!
 
like i typed before. this is hardocp. now for some reason going for the highest overclock is the wrong thing?so disabling ht is wrong. is loosening ram timings to go for higher clock speed wrong also? i am not publishing my results anywhere, am i still "flexing my nuts on the intarweb"? and yes, i know i dont get higher clock speeds with ht enabled. look at post 6.
also check eva2000's results with ht disabled.

http://www.hardforum.com/showthread.php?t=1380110

eva2000 gets new hardware early, and regularly publishes his results here and at xs. he also helps with bios settings and other overclocking tips. is he "flexxing his nuts on the intarweb" also because he is running ht disabled?
 
vanilla_guerilla said:
yes, ht is disabled. runs cooler and overclocks higher in my experience. 20% speed increase with ht enabled? so if i enable ht will i be running at 4980mhz? well anyway i havent noticed any difference in performance between enabled/disabled.
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If you have a highly multithreaded program that can effectively use "8 cores", you will see up to a 20% speed increase over not using hyperthreading. Never said anything about mhz.

In games... not right now, but some programs, like video encoding, 3d rendering programs, photoshop, etc. should see a speed increase with HT enabled.
 
cyclone3d said:
If you have a highly multithreaded program that can effectively use "8 cores", you will see up to a 20% speed increase over not using hyperthreading. Never said anything about mhz.

In games... not right now, but some programs, like video encoding, 3d rendering programs, photoshop, etc. should see a speed increase with HT enabled.
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Video drivers these days are multi-threaded, too.
 
i also disable the other 3 cores. gives me 10% higher clocks, and better superpi times. nuff said.
 
Sure its fun to see how far you can take it but running an i7 without HT is a validation of the netburst architecture. Sure the clock is ticking but nothing is being processed while waiting for data to be fetched. HT on be sure.
 
Hyperthreading is one of the premiere features of the Core i7 as it was on the Pentium 4. You could sometimes get higher clocks on the Pentium 4 by disabling Hyperthreading, but few of us did that and kept the system that way. I don't see why you would disable HT, but if you do, that's your decision. It isn't "wrong" but I see it as being close to disabling 3 of the 4 cores just to see how high you can clock the first one. Sure you will probably get a much higher overclock that way, but it seems like a step backwards to me.
 
lunix said:
running an i7 without HT is a validation of the netburst architecture. Sure the clock is ticking but nothing is being processed
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rofl!! good one...

It's not the size of your clock speed, it's how you use it!!
 
Brahmzy said:
Also, does is the i7 940 a better overclocker than the 920?
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AFAIK the 940 got 22 x 133 = 2.93 ghz while a 920 got 20 x 133 = 2.66 ghz so I´m guessing it should be easier to get alittle higher with a 940. However if that makes up for the higher price Im not so sure...
 
This is my analogy,

When driving in traffic you see those people dashing in and out of lanes , going faster passing people, putting on the brakes, but low and behold, when you get to the next traffic light, there they are sitting next to you after you have been going slower but in a more calculated approach.

Thank you,
Monnie
 
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