Tutorial #11: Thermal control of Core M 5Y10 (Broadwell)

The first generation Core M was an engineering marvel in terms of the power it managed to fit within the 4.5W TDP envelope. In terms of performance, it sat somewhere in between the 5th generation U-series Core i3 and i5 which bear TDP of 15W but blew both of them out of the water when it came to efficiency. The fanless design not only cut down the weight of the tablet but in fact removed a significant point of failure. My gut feeling is that whirring fans are not a good fit for use cases which involve significant movement à la tablets. On the flip side, the processor package is nothing short of a toaster with its sky high temperature under sustained full load.

This led me to fire up Intel's Extreme Tuning Utility (XTU) on my Dell Venue 11 Pro 7140. Normally, devices in a portable form factor like tablets and laptops leave very constrained thermal dissipation and hence are not good tuning candidates. Hence, unsurprisingly, only the voltage and turbo power controls are on offer in the case of the Core M. After trying out over two dozen profiles, I settled on the following three detailed in the table below wherein I have listed the changes made to the default (reference) settings. Profile 1 aims at a temperature of mid-60s under turbo boost which is akin to what you may find in fanned processors. Profile 2 has turbo boost set to the TDP and allows for sustained usage without thermal throttling. Profile 3 on the other hand is the default profile but with stable under-volting that reduces the temperature just enough to limit instances of thermal throttling under sustained full load.

To check the impact of these profiles, I have used the benchmark within XTU (XMarks) as well as the CPU stress test (duration of 1 min). Additionally, I have used the CPU Mark and 3D Mark tests of PassMark as they seemed to be particularly responsive to the changes. Lastly, any CPU test would be incomplete without CPU-Z and hence its bench also makes an appearance.

As can be seen from the table above, there is a compromise to be made between temperature and performance depending on what floats your boat. In my case, I decided to go with 'Profile 3' for now since sacrificing power in a mobile device is always a tough choice. Even then, it is an improvement over the default profile in terms of performance as well as temperature. Profile 2 seems like an especially good option in case thermal throttling is a major concern while Profile 1 plays it really cool if you cant't warm up to the idea of using the tablet as a finger heater. Overall, I am to this day impressed by the Core M package, enough to have it don a triple avatar.


Laurie McKinlay said...

Great article and good research, yes the Core M chips are some of the best for tablets. Your 3Dmark GPU seemed to benefit as the 5Y10 is already at 2GHz limit, but if you had the 5Y71 version you would also see improved CPU scores. It's also possible to add an extra copper layer under the heatsink to improve cooling (and turbo boost clock speeds with the 5Y71).

Sa Ma said...

Thanks for the compliment. The 5Y10 in the Dell 7140 is especially thermally constrained due to the plastic back cover which results in poor heat dissipation. This was all but a cheap means of getting a bit more out of the device. However, the latest Spectre and Meltdown updates have certainly ensured that all gains are wiped out and then some. I don't suppose I will go with the Y series ever again.