core i5 750 clock speeds

[h0ll0w]

So I have a core i5 750 on a P55M-GD45 mobo and I'm seeing something which seems a little funny. I am not in the habit of checking the clockspeed regularly, but today I noticed it runs at 1200mhz, which I presume is because of speedstep or whatever downclocking it when it's idle.

So to double check that the cpu runs at its normal speed when under load, I download and run prime95, which is what the first google result provided for cpu stress test. Sure enough it jumps up to 2.8ghz, which is what I expected.

The funny part is when I stop prime95, the clock speed jumps between 3.0 - 3.2ghz, the multiplier between 23-24. WTH, I would expect the clock speed to drop, if anything, after being cranked to the max by prime95 for a while. And it seems to be stuck on 3.0-3.2ghz even after a restart. The bus speed is 133mhz.

Why is this happening ? Is this my crappy mobo losing the plot ?

 

[shovenose]

Disable the power savings features in your bios

 

[FrancTheTank]

Run Intel Burn test to put max strain on your CPU.

Not sure why its not dropping speed after???

 

[kyton]

Have you checked that you have the latest bios on the motherboard. I also have the i5-750. Under normal load it is at 2.66ghz. Speedstep has to be enable for it to utilises Turbo Boost. Goes up to max 3.2ghz depending on the application and number of cores it needs for the app.

 

[P924]

Are you sure there are no processes using cpu after you stop the test? Turbo boost only goes up to 3.2ghz if only one core is used...

 

[h0ll0w]

I found out just now that this happens when I enable High Performance in Control Panel > Power Options.

If I put it on balanced it idles at 1.2ghz and jumps up to 2.8ghz when running Intel Burn test. Also when the test is stopped it drops back to 1.2ghz as it should.

So I guess we can close the file on this one The high performance power option probably just kicks the mobo/cpu into overdrive. (As the name suggests )

 

[Pada]

EIST (Enhanced Intel Speedstep Technology) would dynamically adjust the CPU Multiplier such that the speed changes between like 1.2GHz - 2.67GHz.

Then the Turbo Boost can then boost the speed even more, where it can increase 2 of the 4 cores by 133MHz, and the other 2 by 532MHz, which would result in your CPU maxing at a frequency of 3.2GHz without overclocking at all.

Have a look at the specs of your CPU here, which is where I got all my info from: http://en.wikipedia.org/wiki/List_of_Intel_Core_i5_microprocessors