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Laptop Undervolting Adventures  

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Goatenstein
(@goatenstein)
Active Member Registered
Joined: 4 months ago
Posts: 31
August 6, 2019 19:26  

Hey all,

I have an Acer Predator laptop that has an i7 7700HQ and a GTX 1060 6GB. It has always run a little hot and loud, so I’m trying to fix that with undervolting.

I will be using Intel’s XTU software for my CPU. An undervolt will be applied and then Cinebench R20 will be ran to get rough performance numbers. I will be using XTU as a hardware monitor.

Here’s a table of my Cinebench results.

Voltage

CB Score

Clock Speed

Power Draw

Temperature

Stock

1623

2.79-3.38 GHz

25-41W

70-89C

-40mv

1736

3.38 GHz

36W

87C

-80mv

1734

3.38 GHz

34W

84C

-100mv

1721

3.38 GHz

32W

81C

-120mv

1724

3.38 GHz

30W

79C

-140mv

1718

3.38 GHz

28W

78C

-150mv

1724

3.38 GHz

27.5W

76C

At stock voltage, my CPU’s clock speed, temperature, and power consumption would fluctuate wildly. I suspect I was hitting a combination of temperature and power limits. Lowering the voltage made all those stable, which increased my score.

I was impressed with the temperature and power improvements. Going from -40mv to -150mv lowered my temps from 87C to 76C and my CPU power from 36W to 27.5W. Very impressive!

I ran Prime95 with small FFTs at varying voltages for stability checks. I saw some interesting results on the hardware monitor. At stock, my clock speed rarely jumped above 2.79GHz, but I was constantly hitting thermal limits. The power, temperature, and clock speed graphs would have occasional spikes. At -50mv, there were more spikes, but less throttling. At -100mv, the spikes became very regular to the point that my graph looked almost like a sine wave. There was no thermal throttling. At -150mv, the spikes stopped. I hit 3.38GHz, 39W, and 88C and stayed there.

I will need to run more stability tests. Right now, I’m happy with this undervolt, so I don’t think I will try to push it any farther.

Next time, I will try it on my GPU.

"There are no solutions, there are only tradeoffs"
- Thomas Sowell


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Goatenstein
(@goatenstein)
Active Member Registered
Joined: 4 months ago
Posts: 31
August 6, 2019 20:29  

Quick update,

I have encountered some instability, so I backed the voltage down to -135mv. This seems very solid so far.

"There are no solutions, there are only tradeoffs"
- Thomas Sowell


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