CPU multiplier low under load

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jancoz

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Jul 9, 2013
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I'm trying to overclock my CPU from 4.7 GHz to 4.8 GHz or higher.

My PC runs fine on 4.7 GHz, stress test and all. When I put the multiplier on 48 it still at first sight runs fine but then when I benchmark I get a lower mark than on 47 and see that when under load the multiplier doesn't go above 45. The weird thing is that when the CPU is idle the multiplier does reach 48. I've tried playing with the ring multiplier and with the voltage but to no effect.

Anyone any idea what might be the issue here?

Details:
CPU: Intel i5 6600k
BIOS is up-to-date
 
Solution
J
This sounds like an unstable overclock.
What are you USING to overclock? I had stability issues when using Intel Extreme Tuning Utility but not my Gigabyte BIOS. With IXTU, it was only clocking 100mhz under my specified frequency, but was nonetheless.
It's possible that your specific processor cannot overclock over 4.7ghz safely. The Turbo Frequency is only 3.9ghz by default, so anything significantly over is already good. Eventually you might need to increase the voltage so much to achieve a stable overclock that you'll end up frying your CPU.
Going over 1.4V Vcore for that Intel i5 6600k is generally unsafe, especially when considering the longevity of your processor (even with adequate cooling).

What are you setting your...
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jancoz

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I do monitor the temps, and they never exceed 65 degrees, so I can't imagine it throttles.
And I just use CPU-Z's stress/bench, it's not very accurate but it's handy when quickly wanting to determine whether an overclock works or is pretty stable.
 
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Barty1884

Barty1884

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What are your full system specs?

What kind of voltage are you using for a 6600K to be hitting 4.7-4.8GHz and staying <65'C? That's pretty impressive (if it's stable).

CPU-Z stress, in my experience, will only catch the OC's that are already borderline unstable. Something like OCCT, Aida64 or older versions of Prime95 would be better options IMO.
 
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jancoz

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CPU: Intel i5 6600k
GPU: NVIDIA GTX 1080
Motherboard: MSI Z170M Mortar
CPU Cooler: Corsair Hydro H55

I'm running 4.7 GHz at 1.425v atm.

I tried using Aida64, as you suggested, and I came across something odd. If I would stress just the CPU then the clockspeed would be a constant 4.7 GHz but if I would also check "FPU" then the clockspeed would be somewhere around 3-3.5GHz, but maybe this is normal, I don't really know tbh. Also, temperatures during the tests did not exceed 60 degrees.
 
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jerrylee22

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Aug 31, 2016
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This sounds like an unstable overclock.
What are you USING to overclock? I had stability issues when using Intel Extreme Tuning Utility but not my Gigabyte BIOS. With IXTU, it was only clocking 100mhz under my specified frequency, but was nonetheless.
It's possible that your specific processor cannot overclock over 4.7ghz safely. The Turbo Frequency is only 3.9ghz by default, so anything significantly over is already good. Eventually you might need to increase the voltage so much to achieve a stable overclock that you'll end up frying your CPU.
Going over 1.4V Vcore for that Intel i5 6600k is generally unsafe, especially when considering the longevity of your processor (even with adequate cooling).

What are you setting your Uncore/Cache to? You might know this, but you want to keep it within 200-300mhz less of your core clock, and if you're experiencing stability issues, you might need to tune this back.
There's also the idea of the silicon lottery and that some processors can or can't do certain things.

Your processor is already exceeding expectations, and pushing it further likely isn't worth it.
 
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Solution
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Juseh_

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Aug 23, 2016
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ITs just a suggestion but I think you have the same issue than me. My temps are kindergarden level, i go to 4.2ghz and render speed is the same or worst than 3,9, no matter voltage.

So probably throtling for "an expert would know" reasons
 
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