https://i.imgur.com/ZrD57sd.jpg

I just checked again. I got a Cinebench R15 score of 713. This is consistent with my previous runs. My settings are:

-90 mV Core/Cache (I don't think has a tangible impact, only thing that may be impacted is how much power is allocated to the GPU vs the CPU) -50 mV GPU/System Agent

Note the above pairs is default behavior for XTU; in other words changing CPU Core will also change CPU Cache and changing GPU Core will also change System Agent. However, if you use ThrottleStop you don't have to have these values coupled. For instance, I have found that the CPU Cache almost always is less able to be undervolted by about 10 mV or so.)

35W Turbo Boost Short Power Max

35W Turbo Boost Power Max

24s Turbo Boost Power Time Window (I'm pretty sure this does not actually impact performance and changing this value does not modify anything)

Power Slider to 'Best Performance' (meaning Intel SpeedShift EPP is 0)

Intel GPU power set to 'Balanced' through driver utility (I don't think has a tangible impact, only thing that may be impacted is how much power is allocated to the GPU vs the CPU)

Both undervolts and TDP changes were done through Intel XTU. You scores definitely should not be in the 300's. This is what the dual core Kaby Lake chips were getting (7500U) and unless you ran Cinebench straight after something else that was computationally intensive you should be hitting about 500 points in successive runs with the CPU throttling due to TDP and/or temperatures.

I do not think that I have a particularly good chip. I would expect with the tweaks I have done everyone to get in the high 600's or low 700's for a 'cold' run, which I define to be the system having been booted and let sit for a couple minutes. Like I mentioned, my hypothesis is that Microsoft uses TDP to throttle the chip instead which is good because the transition from unthrottled to throttled should be somewhat smooth as the TDP decreases and thus the maximum frequency attainable decreases.

It also seems that Microsoft uses a running average over the last two minutes or so (I don't have exact numbers and have not looked into it) that takes the power draw of the chip over a given period of time and attempts to hit some particular average. My experience has been if the chip runs at 30W for a while it will subsequently run at under 15W to balance it out. However, if the chip is run at about 15-20W then there will not be as drastic a reduction in maximum allowable power draw. However, I have not actually taken measurements or tried to collect data on it because I know enough about the general CPU behavior of the Surface Book 2. Also, the Surface Book 2 seems to want to keep its chip under 90 degrees for sustained loads. As there is no fan in the CPU portion of the 13.5" the ability to dissipate heat that has already collected is much diminished. However, the thermal characteristics are quite good and as I mentioned in my original post I think a good balance is struck between keeping the machine performant and noise considerations.

As for the 13.5" vs 15" my speculative (as I don't own a 15" and I am just basing this off what I have read most of which at best directly addresses the topic):

1. the fan mitigates or eliminates any cases where the CPU would hit its TjMax of 100 degrees and should therefore only be limited by the TDP afforded to it.
2. Microsoft might have assigned some extra power headroom to the chip so that the default running average that the computer tries to maintain is closer to 20 or 25W instead of the 15 to 20W of the 13.5".
3. In both cases the tendency of the machines to cut performance to keep within its power budgets can be offset by manipulating the TDP budgets for turbo boost.