Strange Core i7

palladium

Senior member
Dec 24, 2007
539
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Just got my core i7 (920) rig, wanted to see if my system is stable at stock before I start OC it. I ran CPU-Z, Coretemp and 2 instaces of LinX ( max out all 8 cores). Strangely enough, CPU-Z showed that my CPU is running at 2.8GHz (21*133) - even after maxing all 8 cores for 1 hour - here. Coretemp, however, showed the CPU running at 128.51*21=2.7GHz. The core temps at full load are 70/69/69/70. My other parts are:

Gigabyte EX58-DS4
6*2GB Kingston ValueRAM DDR1333

I did not overclock in any way. ( everything was left at default). Bios report: 20*133.

I thought turbo boost only works if only 1 or 2 cores are loaded and the rest are idle, but in my case it seems to work even after I max out all 8 'cores'.

Is this a bug?



 

AnnonUSA

Senior member
Nov 18, 2007
468
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As long as the chip remains in it's thermal envelope, performance should not be touched.
 

Idontcare

Elite Member
Oct 10, 1999
21,110
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Originally posted by: palladium
Just got my core i7 (920) rig, wanted to see if my system is stable at stock before I start OC it. I ran CPU-Z, Coretemp and 2 instaces of LinX ( max out all 8 cores). Strangely enough, CPU-Z showed that my CPU is running at 2.8GHz (21*133)

Assuming you have the latest CPU-Z it will correctly report the CPU multiplier and Bclock that is actively/currently being used at the time you observe the CPU-z screen.

Your i7 920 is programmed to allow a multiplier as high as 22x (for 2.93GHz) so long as the heat output and temperatures of the CPU are within the thermal guidelines that Intel programmed into the CPU.

Yes the base multiplier is 20x, and the chip will operate at the multi if and when you run a program that causes enough heat output to push the CPU close to its allowed thermal limits.

Try running Prime96 small FFT and see what happens in CPU-z.

Coretemp is a little flaky about reporting the most recent P state of the system, sometimes it gives screwy results, best not to worry about what coretemp tells you regarding the bclock and cpu multiplier.
 

rge

Member
Feb 18, 2008
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Gigabyte bios F3 On Ext and UD5 have TDP limit enabled, so in turbo mode you will have a 21 multi (turbo) with 1 or 2 cores heavy loaded or even 4 cores lightly loaded. But prime with more than 3 cores and turbo will disengage and be back to stock multi of 20.

On all f4beta and newer bioses, TDP limit is disabled, so turbo mode = max multi +1. With turbo enabled, you can set 20x multi, you will always have 21 multi regardless of load, just like I will have 23 multi on my i940 regardless of load. In fact you can set multi to 15 and you will still have 21 multi. Turbo is set via MSR register in cpu as 21 max, so turbo enabled = always 21 multi i920 and always 23 for i940, on Gigabtye boards. P6 Asus handles turbo differently. Intel mobos some let you play with TDP settings.

So all depends on whether the current bios you are using has the TDP limit enabled or disabled (hidden setting in GB, you cant change it, though many have requested GB bios makers to let us play with it...we will see) . (there is an intel white paper explaining turbo, primarily limited by TDP in W, but also by current and temps, but only if bios chooses to turn on such limits or turn off as in GB case...or partially employ them as P6 seems to do).

If you ever want to see +2 multi turbo on either i920 or i940 you have to disable all cores but 1 in the bios. Which makes the +2 turbo multi worthless. That again is via testing via intel white paper and the actual MSR register reads for my i940, 23,23,23,24 ...24 being active only if 1 core is active and all others turned off.

But cpuz is reading correctly most of time...its your bios that is likely not following TDP limits, much to the pleasure of all i920 owners who now have a 21 multi, which makes getting 4 to 4.2 much easier.

Edit: and like idontcare says, coretemp mhz is bugged
 

palladium

Senior member
Dec 24, 2007
539
2
81
Your i7 920 is programmed to allow a multiplier as high as 22x (for 2.93GHz) so long as the heat output and temperatures of the CPU are within the thermal guidelines that Intel programmed into the CPU.

Yes the base multiplier is 20x, and the chip will operate at the multi if and when you run a program that causes enough heat output to push the CPU close to its allowed thermal limits.

Is that thermal limit the 'tjmax'?

Try running Prime96 small FFT and see what happens in CPU-z.

Still 21 multiplier- as per rge's post. Oh well, it's not a bad thing :)
 

rge

Member
Feb 18, 2008
50
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0
If you hit tjmax the cpu will throttle, decrease mhz, but that is not the turbo thermal limit mechanism, that is just thermal throttling.

I had posted the intel white paper on turbo in below thread back when beta testing programs as trying to get accurate mhz. But turbo is primarily limited by TDP, though has secondary limits current and temp. One irritated Asus P6 owner was complaining everytime he reached 85C turbo kicked out...again Asus implements turbo very differently than Gigabyte.
http://www.xtremesystems.org/f...3464222&postcount=2690

On the TDP limited bios F3 for Gigabyte, if you use everest most recent beta build (on forum not from main download page) it seems to read watts (TDP) correctly on i7. Soon as hit ~115W TDP (rated max 130), turbo disengages and back to stock multi. On f4 beta bioses, where limits turned off, you can run cpu at 95C turbo wont disengage, you ran run prime 95 small ffts + 2 instances linpack on overclocked overvolted cpu and hit 155W TDP, turbo still wont disengage.