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RussMaf
Fanfold Paper
Posts: 4
Registered: ‎03-30-2018
Location: US
Views: 3,568
Message 1 of 5

TDP Throttling on 8250u and 8550u

I would like to know why Lenovo decides to lockdown the power draw of these cpus even if they are on AC power. I recently purchased the Lenovo flex 5 and I love the build quality of the laptop, it is in my opinion the best built 2 in 1 for the price range compared to any other brand. So I got it home and of course starting the typical setup of a new computer. I was doing all the windows 10 updates and noticed that it was taking a lot longer than another laptop with similar specs. So after all that was done and everything was up to date I decided to run a benchmark on the cpu to see exactly how much slower it was running than another laptop with same cpu. And the result? Nearly half more than half the speed of the other laptop.

 

Now the I5 8250u that is in both of these laptops have a base clock of 1.6Ghz and a boost of 3.4Ghz with 4 cores and 8 threads. It is a very capable processor and nothing like it has ever been available in typical small form factor laptop. This was made to be my number 1 condition on a new laptop. It had to have this new processor. I love the idea of having a laptop for portability but have always hated how much slower they have been compared to their desktop counterparts. It was finally all going to change with these new processors. Yet not on this laptop. 

 

I noticed that while running these benchmark comparisons the Lenovo never got above 55C which is very strange as it is a small laptop and the cooling cant be that great. Yet the other laptop was hitting 90C which is hot yes but when a benchmark gets nearly 100% better results it makes perfect sense. So obviously the Lenovo had to be throttling somehow but I couldnt quite figure out why because the thermals had more than enough headroom and it was on AC power with max performance setting. So I started looking in to what is happening further. After some diggin I realize that the 3.4Ghz boost clock was only being used for 28 seconds at a highest 25 watts then throttling down to the 15 watt TDP. Where as the other laptop was keeping 30 watts steady as long as the CPU was under 95C. This translated into higher temps but EXTREMELY higher performance as well. The boost and base clocks are so far apart that the performance is really degraded if not allowed the extra power.

 

So I dont mind the power being throttled while on battery as it would kill battery life. However even on battery there should be a way to allow the CPU to go as high as it can if thermals are in check. Especially if we have an option to run it lower to save battery or higher to get the performance. As of now the performance slider in my opinion does nothing as it has no noticeable power draw difference or performance difference so why is it even there? I want to be able to choose between my performance and battery. Lenovo please unlock your power draw or at least give us an option in the bios for us to unlock it ourselves and deal with the power draw on our own. I got this laptop because of the processor and its build quality, but if I cant use the performance that the processor was meant to provide I would rather get slightly less build quality and get all the performance allowed by these amazing chips.

gnusmag77
Punch Card
Posts: 24
Registered: ‎01-02-2018
Location: PH
Views: 3,455
Message 2 of 5

Re: TDP Throttling on 8250u and 8550u

I have one word for you (or two rather?) Throttlestop - it will basically solve your throttling issue and unleash this processor's true potential.

Use at your own risk, even though there is not much (unless you really push setting to the extreme, and even then, there is a built in max TDP autoshutdown that will protect your laptop and cannot be overridden).

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RussMaf
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Posts: 4
Registered: ‎03-30-2018
Location: US
Views: 3,446
Message 3 of 5

Re: TDP Throttling on 8250u and 8550u

Thank you for the reply unfortunately that was my first idea as well however even with throttlestop it will not go over 15 watts of usage. I was able to undervolt however and that did increase my clock speed from the base 1.6Ghz to a much better 2.3Ghz but I still would like to get the full output if possible. Sadly the bios is locked down so hard that it is not possible to increase the turbo boost length or increase power output during normal operation. If there is something I am missing I am all ears but I don't see how to unlock this bios to keep it at boost levels constantly. 

nesbej
Paper Tape
Posts: 3
Registered: ‎02-10-2018
Location: US
Views: 2,863
Message 4 of 5

Re: TDP Throttling on 8250u and 8550u

I've also found it basically impossible, even with throttlestop, to get above 15W for prolonged usage. This is on the i7-8550u 720s 14IKB.

 

It's really a shame as I have a lot of thermal headroom after doing a re-TIM, I don't go above 62C. 

orz1943
Paper Tape
Posts: 1
Registered: ‎01-18-2019
Location: TW
Views: 586
Message 5 of 5

Re: TDP Throttling on 8250u and 8550u

I got my ideapad720 (i5-8250u) last month,so i have the same problem.Try Xtu and throttlestop change the PL1 and PL2 but not work.Lenovo lock the bios TDP!!!!Lenovo should unlock the bios.

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