# [SOLVED] i5-2500k throttling under prime95 test on asus p8z77?



## jamiemac2005

Hi everyone, I have recently bought a new computer, and recently began the task of overclocking the system and stability testing it.

I have managed to make the system stable at 4.2GHz(102 MHz with x42 multi), however when I go to stability test the system (using prime95) the processor starts throttling during the 4th test dropping the multiplier down to 35 then 16.

Normally i would fix this by increasing the TDP however i can't find a way to do this on my new motherboard and i can't find many resources which describe the process of overclocking the i5-2500k on the Asus p8z77...

I was wondering if anyone could give any advise as to what is causing the throttling and/or what could fix it? Or any advice as to how to stability test my system without it throttling?

Many thanks for any help anyone can give,
Jamey


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## darfvayda

*Re: i5-2500k throttling under prime95 test on asus p8z77?*

Look for SpeedStep in your bios, disable it. Set your power plan in windows control panel to High Performance (you may need to click 'show additional plans' cause they try to hide that sucker!)


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## greenbrucelee

*Re: i5-2500k throttling under prime95 test on asus p8z77?*

Please post your full computer specifications inlcuding make and model of power supply.

If your system is oem i.e one you have bought from a shop such as a dell, hp or compaq please post the model number.

Posting your specs can help us to help you better.

I overclock all the time with your cpu including a decent cooler and power supply you should be able to start of with a 45 x multiplier with no problem. Please post the info requested.

darfvayda is correct in a way that you should switch off intel speedstep but if you get the oc right then you can enable it later. Most likely you have a voltage or temp issue.


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## jamiemac2005

*Re: i5-2500k throttling under prime95 test on asus p8z77?*

Hi, thanks for the advice, I've disabled speed step and my windows 7 settings are set to high performance (modified to literally not save any power). After re-attempting the prime95 test the processor still throttles on the 4th test first down to x35 then slowly down to x16 and jumps back up to x45 when i stop running the prime 95 tests.

My assumption would be that it has something to do with the max tdp (from other posts on the subject on other forums) however I cannot find a mobo bios setting to modify the TDP or that affects or mentions throttling in the manual. The DIGI VRM+ Settings are modified to extreme and the CPU current capability is set to 120% (The max setting available) as advised on a similar question on a similar site. However the problem persists.

I should note that when running games at near-full load that the problem doesn't occur (from what i can tell).

Thanks for the input greenbrucelee, my thoughts were the same. The specification is as follows:
- *PSU:* Corsair GS500.
- *MoBo:* Asus P8Z77-V LX
- *Processor:* i5-2500k
- *Graphics Card:* Nvidia GTX 550ti
- *CPU Cooler:* Cooler Master 612S with 2x120mm cpu fans running at 12v
- *Other Cooling:* 2x120mm intake [email protected] + 3x120mm exhaust [email protected]
- Also 1x 1TB Sata HD and 1x DVD/rw and a 300Mbps NIC on PCI, and power being drawn from 2xUSB for mouse and kb.
- Should probably mention it's running Win 7 Home premium
- And it was "custom built" inside a cooler master elite 430 black case so it's not an OEM build...

It runs at max 52-54 degrees centigrade under full load @ both 3.7GHz and 4.2GHz (achieved by using the Ez bios settings high performance mode). Note: The processor still throttles using the Ez-mode settings so i'm uncertain of the issue.

When i run my spec through a PSU calculator with the OCed information (1.3 vcore, 45x multi, 102mhz base clock [again auto clocked]) at 100% load and 80% efficiency it calculates that the max wattage it should be using is around 438W but i'm unsure of how useful that actually is. I may be making a mistake or i may misunderstand the full capability of my PSU?

To OC the board i have attempted to use similar settings to a guide i found on OCing the i5-2500k on an asus p8z68 whilst also thoroughly checking the other possible bios settings and disabling any power saving and ensuring that anything limiting the amount of power the cpu gets is disabled/minimized and the problem persists. I'm certain i'm either missing something or my method is off...

As mentioned earlier i found a forum post after googling "i5-2500k multiplier drops" on an asus p8z67/68 which seems to have a similar issue here: Multiplier drops under stress test - AnandTech Forums however the original poster tried everything i have tried and then didn't stress test to confirm, to avoid damaging the board/chip so the topic was dropped.

I'm away from the computer currently but tomorrow i will check that i'm running the latest bios, if i'm not i'll flash to the current version i'll also take a fresh look at the bios settings to see if i can find something i'm missing.

Also I should mention that running CPU-Z shows a TDP of 95w, which i think could be the cause of the issue (as described in the other thread, TDP hits 95w, needs 130ish then throttles?) but i cannot find a fix for this? I have both tried with EIST enabled and disabled and i've also attempted to set manual values for the power limits and current limits (however i'm uncertain of what the current limit should be). I'm also uncertain of how to work out the load (wattage) and voltage being used by the pc but i'll get to checking this tomorrow.

Any more help would be brilliant, as i mentionned i'll get back to trying to sort this again tomorrow.

many thanks for your input so far,
Jamey


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## greenbrucelee

*Re: i5-2500k throttling under prime95 test on asus p8z77?*

Add 30% to 438w.

When you get a psu the recommendation only accounts for the gpu not the enitre system or peripherals you might have attached. This also accounts for ripple and component degredation.

You have a corsair psu which is a good name but what many people dont know is that the gc and cx units are not made by seasonic thefore making them low quality.

If I were running your setup I would be running a 650w seasonic made psu and if I was overclocking t the max I would go for atleast 700w.


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## jamiemac2005

*Re: i5-2500k throttling under prime95 test on asus p8z77?*

Ahhh okay, brilliant, thanks for the help. I was afraid that could be the case. Running stock clocks doesn't cause throttling under general use so it will suffice until i can get a hold of a better psu. I intended to build with a 650w psu however the stockist i was using didn't have it in stock...

Thanks again,
Jamey


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## Tyree

Also note-Speed Step is there for protection of the CPU. It throttles back the CPU when demands are low and that saves power, reduces stress on the CPU and makes for a longer life of the CPU.


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## jamiemac2005

Yeah I had a good read of the mobo manual and re-enabled speed step and checked it was doing its job...

I'm running the processor at 3.7GHz stable @ 30 degrees centigrade and having no issues. When I have the money spare I'll upgrade my PSU to something with a little more oomf.


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## greenbrucelee

With the i2500k you should be able to start off with a x45 multiplier with no issues what so ever if you have an aftermarket cooler such as the BeQuiet Darkpro advanced and a decent 650w psu. But as with all overclocking it is best to do things in stages so start at 40 for each core.

Make sure your ram voltage is at 1.5 or whatever it is the manufacturer states and you should increase the cpu vcore to aroung 1.3 and raise in increments after each reboot. 1.5v is the max but I would not go above 1.4.

Your base clock has the possibilty of being changed to 105 but do this in small increments and start at 100.


Disable: 

Limit CPUID Maximum
Power Technology
C1E Support
OverSpeed Protection
Spread Spectrum


Enable:

Internal PLL Overvoltage
Execute Disable Bit
Intel Virtualization Tech

This is just a quick reference of the top of my head. I will do a proper how to in the overclocking section soon just like my how to overclock a core 2 duo or quad thread.


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## Tyree

I would very strongly suggest you remove any OC until you replace that lower quality underpowered PSU with a 650W minimum good quality unit.


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## darkfire3814

Any word on a guide for overclocking a i5 2500k on a p8z77-v lx mother board?


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## greenbrucelee

darkfire3814 said:


> Any word on a guide for overclocking a i5 2500k on a p8z77-v lx mother board?


I will do one soon although overclocking the 2500k is basically the same for any board just some boards might have an extra feature or may not have an extra feature.


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