So far all 10th gen Intel laptops I’ve tested can’t be undervolted with Intel XTU or Throttlestop, presumably due to the Plundervolt vulnerability. I’m not certain, but think that undervolting in BIOS should still be possible, as long as the BIOS supports it.
After skimming the Plundervolt whitepaper it sounds like the bug is exploited through the software’s ability to apply undervolting. With the Gigabyte laptops I tested I didn’t see a way of doing that in the BIOS, and by default the GS66 doesn’t offer this either, that is until you enter the advanced mode, which is as easy as pressing Right Shift + Right Control + Left Alt + F2, obviously.
Once in this mode, go into the advanced settings, scroll down to the overclocking performance menu, enable the overclocking feature,
then from here you can change XTU interface from the default of disabled to enabled. Interestingly there are no warnings about security issues or anything when changing it, it just lets you enable it.
We’ve also got the option of undervolting the CPU through the BIOS itself, so this can be done even without using software like XTU or Throttlestop if you prefer. Personally I prefer software, so have enabled XTU Interface, it’s easier to recover from when things aren’t stable.
It makes perfect sense that we get the option to change these things in the BIOS, it’s an unlocked K processor, so I’d be disappointed if that wasn’t the case. That said, fortunately this feature isn’t limited to the GS66 laptops with K CPUs, Tim from Hardware Unboxed confirmed that the i7-10750H model of GS66 also allows you to enable undervolting and undervolt through the BIOS in the same manner.
After saving the settings and booting into Windows, I confirmed that undervolting was now unlocked in XTU and worked as expected, so let’s check out some revised thermal testing and see how this helps.
All testing was done with an ambient room temperature of 21 degrees Celsius.
The stress tests were done by running Aida64 with only stress CPU checked and Heaven benchmark at the same time, while the gaming results were done playing Watch Dogs 2.
More games benchmarks on MSI GS66 and MSI GS66 Thermal Testing
I didn’t try to tune the undervolt and just selected -0.1v, a value I’d expect most to hit no problem. We can see that temperatures haven’t really changed on the CPU when under stress test, but the GPU gets a bit cooler, presumably due to the shared heatpipes, changes to the CPU do affect it. In the games we were just seeing slight 1 degree improvements on the CPU, though more of a change to the GPU temps.
I’ll also note that although the thermal throttle limit is set to 95 degrees celsius, I did see the option to boost this in the BIOS. While I could have done this to squeeze out some extra performance, I probably wouldn’t recommend it just for longevity, 95 is already a fairly high limit in my opinion, if it were my machine I might be more inclined to cap it to 90 instead. Regardless, it’s cool that the option is available in the advanced BIOS.
These are the clock speeds for the same tests just shown. 
We’re seeing a nice boost to the CPU performance, especially in the stress tests, around a 300MHz boost over all 8 cores for such a simple change isn’t bad at all.
The games also saw a similar fair improvement, I think with all improvements in place the 4.4GHz all core turbo boost speed was being hit. It was interesting that it didn’t go higher, because XTU reports the all core CPU boost speed as 5.3GHz, so there may be some setting in the advanced BIOS that needs to be adjusted to affect that. Either way, I can’t complain about this performance especially when you remember the CPU was at 83 degrees here.
When looking at the TDP reported by hardware info we’re not seeing too much change here, and this is because the power limit was still being hit, but the undervolt allows us to get more done within the power limit available.
Boosting the power limit in XTU didn’t do anything to help, even though PL1 is set to 65 watts, so I might need to get into the BIOS to boost it up further. The power limit dynamically boosts up as thermals improve, which probably explains why the power limit boosted in the stress test with the undervolt applied, it was running cooler.
Here’s how Cinebench performance improves with the same undervolt in place. 
It was possible to boost the multicore score by 11% with this honestly pretty average undervolt, you could definitely push it harder.
CPU only clock speeds improve a similar amount with the undervolt in the Aida64 stress test. 
We’re still power limit throttling, however the undervolt allows us to get more work done within the power limit. 
The undervolt also drops the temperature just a little extra despite also offering better performance,
so you could definitely take advantage of this and mod the GS66 further with the billion options in the BIOS if you know what you’re doing.
There are plenty of settings in there so you can tune until your heart's content, but as bob of all trades mentioned on twitter, if you don’t know what you’re doing you could do some damage. Let me know what you thought of the improvements by undervolting down in the comments.
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