Got an i5-10400 drawing 20 watts more than tdp during stress test

[Maxstate]

Hi, thanks again for throttlestop. It's saved me money, given us back control over our hardware to some extent, and been a catalyst in learning about a ton of stuff.

Short question: recently bought a new computer for my partner. It's a small form factor case so I decided to make the best of it and run her hardware as efficiently as I could for thermal reasons. After a few hours of tinkering and a few days of stress testing, I'm satisfied with the result: never thought an SFF machine could run cooler than my old open-cased workhorse.

I noticed that the i5-10400's tdp went up to 85 watts during prime95's toughest test. It's supposed to be a 65 watt tdp cpu. Is that normal? I did change some limits in the TPL screen but never expected them to actually do anything (the cpu is heavily locked down). Ts bench stayed around 63 watts.

What is happening? Is it actually requiring that 85 watts and using it, or just drawing it for the heck of it? Its effective frequencies haven't changed. So, assuming that I somehow 'allowed' this, I'm wondering whether there's any benefit here, or whether I should cap it to 65 in the TPL screen?

Is this the turbo popping off on all cores or something?

Thanks for your time again.

 

[unclewebb]

Most people do not realize that the Intel TDP rating is measured at the base frequency which is only 2.90 GHz for an i5-10400. If you enable turbo boost and run a stress test beyond this speed then it is normal that the CPU is going to want to consume more power.

If you or the BIOS lock the turbo power limits to 65W, the CPU will have to throttle so it does not exceed 65W. Using ThrottleStop or the BIOS to increase the power limits allows the CPU to run at its full rated speed. If you like performance and have adequate cooling, increasing the turbo power limits is highly recommended.

What is happening?

Power consumption depends on what software you are running. Prime95 uses lots and lots of AVX instructions which consume a lot more power.

TS Bench stayed around 63 watts.

The TS Bench does not use any AVX instructions so not surprising to hear that it uses a lot less power compared to Prime95. To wrap your head around this, think about a car going up a mountain grade at 100 km/h vs the same car cruising along at 100 km/h on level ground. Same speed in each situation but obviously going up a big hill is going to consume more energy and produce more heat. Running software that uses lots of AVX instructions is doing the same thing.

whether I should cap it to 65

No need to cap anything as long as your computer is not overheating. Your CPU can run reliably at 65W or 85W. I am pretty sure your partner will not spend all of their time running Prime95 so power consumption in any normal tasks will likely never reach 85W again.

 

[Maxstate]

Most people do not realize that the Intel TDP rating is measured at the base frequency which is only 2.90 GHz for an i5-10400. If you enable turbo boost and run a stress test beyond this speed then it is normal that the CPU is going to want to consume more power.

If you or the BIOS lock the turbo power limits to 65W, the CPU will have to throttle so it does not exceed 65W. Using ThrottleStop or the BIOS to increase the power limits allows the CPU to run at its full rated speed. If you like performance and have adequate cooling, increasing the turbo power limits is highly recommended.


Power consumption depends on what software you are running. Prime95 uses lots and lots of AVX instructions which consume a lot more power.


The TS Bench does not use any AVX instructions so not surprising to hear that it uses a lot less power compared to Prime95. To wrap your head around this, think about a car going up a mountain grade at 100 km/h vs the same car cruising along at 100 km/h on level ground. Same speed in each situation but obviously going up a big hill is going to consume more energy and produce more heat. Running software that uses lots of AVX instructions is doing the same thing.


No need to cap anything as long as your computer is not overheating. Your CPU can run reliably at 65W or 85W. I am pretty sure your partner will not spend all of their time running Prime95 so power consumption in any normal tasks will likely never reach 85W again.

Thank you very much, that all makes sense.

Just for the record: Prime95 topped out at 73 degrees C. Tsbench at 69 C. Using stock cooler, which I repasted just to be sure. I was able to lower core voltage by 163mV and cache by about 60mV. Also lowered igpu and unslice by 30, but the thing has a discrete video card, so I doubt it gets much use outside of simple desktop stuff.

Taking advantage of all this overhead is really a beautiful thing, especially with efficient energy use never being a bad idea.

Thanks again!

 

[unclewebb]

With temperatures that low, I would not bother pushing the undervolt to the edge of stability. Some undervolting is fine but do not get too carried away.

I would not undervolt the Intel GPU or Unslice at all if you have a discrete GPU. No reason to risk stability.