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Core i7 920 2.67GHz - a lie?


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#1
W-Unit

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Hey guys,

So I fired up CPU-Z today and noticed my processor was running at a mere 2.5GHz despite what I thought had been an overclock to 2.9GHz. I decided to reset all the BIOS settings to factory defaults just to sort of get a baseline. After doing so, CPU-Z shows the speed jumping around like crazy. Normally when I start my computer and open CPU-Z first thing, it will sit at about 2.4-2.5 for a bit, then go to 2.67 and try to fool me into thinking all's well. However if I just leave it running and don't do anything else for a minute or two, the speed will jump down into the 1.9-2.1 GHz range and will generally stay around there, with 2008.3MHz being its favorite place to sit.
This is with all factory default settings on the motherboard. The reset operation also reset all my settings in EPU-6 and TurboV, the two programs I have that can tweak CPU and memory settings.

I would like to know how Intel gets away with this. I mean, what, do I have to OVERCLOCK to run at the advertised speed!? Why has nobody else spoken up about this as far as I can tell?
Screenshot attached in case it helps.

Oh, yeah, and when the Core Speed jumps, it usually reflects changes in the multiplier. I thought the Core i7 was supposed to have a locked multiplier of x17 that, if turbo mode is enabled (as it is in the default settings), could go higher under certain conditions, but never lower. Here it is x15, yet sometimes it jumps as high as x20, giving me core clocks of up to a whopping 2.21GHz!!!!

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Edited by W-Unit, 28 July 2009 - 01:03 AM.

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#2
stettybet0

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This is due to SpeedStep. Basically, when the CPU isn't being heavily used, it lowers its clock speed to save power.
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#3
W-Unit

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I see. So when my system starts utilizing more of the CPU, it will automatically start running at the rated speed?

Also, I've overclocked the CPU to what should be giving me 3.8 GHz as I used the exact same settings I saw on a YouTube video that gave that speed, and indeed I do see 3.8GHz when the processor is being utilized more, however I still get the SpeedStep-looking stuff, despite having disabled SpeedStep in the BIOS. It now sits around 3.2GHz and can fall as low as 2.8
The one setting I used that was different from the video was the vCore. The video had this set to 1.35V, while I figured that this was overkill and 1.33V would be sufficient. But voltages have nothing to do with clock speeds jumping around, right?
Disabling SpeedStep removes the option for Turbo Mode from the BIOS, so I assume this means that Turbo Mode can only be enabled when SpeedStep is enabled. So with these two being the only settings that should allow the CPU clock to jump around, why am I still not getting a steady clock reading?

Oh, and one more quick question that's not really related, but not worth starting a new thread over. I was tinkering around and tried setting the BCLK to 200 to theoretically give a clock speed of 4.0GHz (theoretically because of it jumping around), and it worked for a bit, then the PC froze up.
One thing I hate about my case is that it doesn't have a system speaker, so I won't be getting any warning beeps or anything in case of overheating. I'm not too worried about it, though, as I'm limiting myself to 1.35V and I believe my ThermalTake V1 cooler can handle this pretty comfortably (I have it turned up pretty high; I would guesstimate 75-85% fan speed).
But my new question is, does this freeze up more likely indicate too little voltage or an overheat, or something else? I still only had the vCore set to 1.34V when I tried this setting, so upping it to 1.35 wouldn't be a problem if it was the voltage. It'd be nice if someone could tell me the "symptoms" of each type of problem (overheating and insufficient voltage) as I've had difficulty finding this information on Google.

Thanks!

Edited by W-Unit, 28 July 2009 - 02:18 PM.

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#4
Ferrari

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Nevermind, sorry.

Edited by Ferrari, 28 July 2009 - 04:02 PM.

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