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I5 2500K oc Help Please

Last response: in Overclocking
June 16, 2011 7:04:06 PM

Hi guys i wanted to oc my i5 2500k to around 4.5ghz and i got to 4.3 without changing the voltages then went up to 4.4 and ran prime 95 and got an error (FATAL ERROR ROUNDING WAS 0.5 EXPECTED LESS THAN 0.4) so now im back at the stock 3.3ghz
what do i need to do to get to 4.5ghz?
my specs
I5 2500K
Corsair Vengence 8gb (1600)
Amd Radeon 6850


More about : 2500k

a c 150 à CPUs
a b K Overclocking
June 16, 2011 7:27:18 PM

Enable internal pll overvoltage, should do the trick. I'm assuming everything else is on auto and you didn't change other settings since you don't know much about OCing.

Here's the sandy bridge OC guide.
Related resources
a c 150 à CPUs
a b K Overclocking
June 18, 2011 12:30:45 AM

Did you put windows power setting to max performance? Because you have the stress test off and you cpu is not throttling down. You get the same performance at balanced. So idk if CPUZ is saying your core voltage is 1.044 for a throttled down voltage or not but at full load it would be way too low and would cause the error. Stock voltage is 1.3 which should get you to 4.5ghz. It will be listed as "CPU Vcore" in your bios.

If this still doesn't work than look in that guide to what to enable/disable.

Also you should at least be running the blend test over night to make sure you are stable. A couple of minutes is not enough.

What cooler do you have?
June 18, 2011 11:57:35 AM

oh and i have the cooler master hyper 212+ in push/pull and nzxt phantom case so no cooling problems
a c 150 à CPUs
a b K Overclocking
June 18, 2011 10:15:32 PM

So did you try changing the voltage and/or other settings?
a b à CPUs
a b K Overclocking
June 23, 2011 3:01:41 PM

One small edit to k1114: Stock voltage for Sandy Bridge is 1.2v, not 1.3v.

For most Sandy Bridge CPUs, here are the steps necessary for 4.5GHz operation:
1. Change CPU voltage to 1.3-1.35v
2. Change CPU multiplier to 45x
3. Save and Exit

You shouldn't need to fiddle with any other settings, and the PLL Overvoltage setting shouldn't need to be enabled for that low a speed.

The Balanced and High Performance settings in the Power Options make absolutely no difference. I keep mine at High Performance and it still throttles down to 1.6GHz at idle.
a b à CPUs
a b K Overclocking
June 25, 2011 3:32:11 PM

Sandy Bridge was designed to run with those settings enabled. Unless you're going for a bleeding-edge overclock (and no, 4.5GHz isn't bleeding-edge), you shouldn't have to disable them.
June 25, 2011 5:38:02 PM

i done what you said put the v core to 1.33v cracked it up to 45x and ran prime 95 and got the same error on thread4 in seconds =[
a b à CPUs
a b K Overclocking
June 26, 2011 5:14:39 AM

1.3-1.35v is the average, but some require more. Try higher CPU voltage.

You might also be unlucky enough to have one of the Sandy Bridge CPUs that won't do 4.5GHz stable.
June 26, 2011 2:26:59 PM

whats the safest max voltage because i dont wanna blow this thing thanks
a b à CPUs
a b K Overclocking
June 26, 2011 9:27:35 PM

Stay below 1.4v for CPU voltage and below 75ºC for peak Prime95 core temps.
July 12, 2011 8:30:38 AM

hi sorry for late reply yea i got it to 4.1Ghz yesturday and ran prime 95 for 8 hours and no errors now im just trying to hit 4.5 by increasing the vcore bit by bit.
July 12, 2011 11:12:59 AM

Ok i found a problem to get to 4.1 ghz i didnt change the voltage i just enabled a thing or 2 but the bios say my vcore is 1.320 how is that and cpuz says its 1.044 if the stock voltage is about 1v why the hell is my bios telling me that =/
a b à CPUs
a b K Overclocking
July 12, 2011 7:38:46 PM

The CPU goes into low-power idle mode, down-clocking to 1.6GHz and around 1.0v when full CPU horsepower isn't needed in Windows.

The CPU cannot go into low-power idle mode when in the BIOS. That means it's running at full speed and full voltage.

The stock voltage is 1.2v for Sandy Bridge.
July 13, 2011 7:42:53 AM

Ah i was told it was 1v nevermind thanks for the correction so why is it i havent changed the voltage and its showing up in the bios as 1.320 if the stock voltage is 1.2 plus when i ran prime 95 and cpuz and it only went up to 1.056v? How can i tell what the Vcore is its so confusing.
a b à CPUs
a b K Overclocking
July 13, 2011 8:55:45 AM

If the CPU voltage is on Auto, the board will adjust it depending on the speed you set the CPU to. When you set the CPU to 4.1GHz, it automatically adjusted the voltage.

What does CPU-Z say the idle voltage is? The voltage under Prime95 load should be right around 1.320v like the BIOS says.
July 13, 2011 9:21:57 AM

when its under 100 load cpuz says 1.056 when its not under load it goes down to 1.044.
a b à CPUs
a b K Overclocking
July 13, 2011 6:16:08 PM

k2xblazer said:
when its under 100 load cpuz says 1.056 when its not under load it goes down to 1.044.

Okay ... and what does CPU-Z say the idle and load CPU speeds are?

I'm thinking that CPU-Z isn't reading your board right or something. Do you have the newest version?
July 13, 2011 7:24:10 PM

I have cpuz i.58 and the load speed is 4.1ghz 1.056v and the idle is 1.6ghz 1.044v
a b à CPUs
a b K Overclocking
July 14, 2011 5:15:28 AM

Yeah, it's not reading the sensors correctly. There's no way you're getting 4.1GHz on only 1.056v CPU voltage. There are other monitoring programs, so give those a try -- maybe they will read the sensors correctly.
July 14, 2011 8:28:10 AM

Ok dude i had a look around and i tryed speed fan thats not working and Hwmonitor tells me the same story as Cpuz is there any other programs?
July 17, 2011 3:41:19 AM

After all this time messing with your system, and still having issues, why don't you wipe everything and do a fresh install of Windows? With all the things that keep coming up, you're doing something very wrong. Your results just don't make sense.
July 17, 2011 10:50:01 AM

i know man its confusing i mean i formatted my pc about a week ago anyway its just weird how the bios says ive jumped to 1.3v when i havent even touched the voltage
a c 100 à CPUs
a c 235 K Overclocking
July 17, 2011 2:56:43 PM

Try my sig guide, you don't have to run it like that permanently just try it, you may get further using the way I OC mine, what do you have to loose, if it doesn't work try another method.
December 7, 2011 10:16:59 AM

Coretemp, Realtemp or HWMonitor won't be able to read CPU voltage on Gigabyte MBs. Try Easytune6 that comes with your MB. Stock voltage of 2500k is 1.320v. Just put your multipliers to 45x, then use DVID (Dynamic Vcore) to add more voltage until you get a stable 30 minutes (at least) test with P95. Leave everything else on auto. Good luck.