Replying to my own post: this is amusing. I had always had Ol' Paint set up to never sleep, so I had no idea what sort of silliness Apple had been doing with their screensavers. The i7 Mini was still set up for defaults, so I realized this morning that it had gone to sleep with the default Sequoia animated redwood forest scene on my two 4K displays.
I was downright gobsmacked at how much power that wastes. Idling-but-awake, the machine dissipates ~8W on average. When that silly "screensaver" fires up, it burns ~45W average, all in the gfx hardware and RAM, and the fan must run at 3400rpm (using Macs Fan Control with a span of 65degC-99degC, on the PECI sensor)! This is
madness: the CPU temp goes back up into the upper 80s, all while accomplishing nothing whatsoever. That is approximately
one-third of its wide-open-loaded dissipation. The screen grab here from the Intel Power Gadget tells the tale: this is what happens to the power dissipation when you wake it up from its "sleep". Easy fix: no more sleep.
I realize that this is relatively trivial, in the cosmic scheme of things. But, part of the goal of this exercise was controlling power dissipation, and managing the resulting cooling needs. Going from burning ~750W with the 5,1 at idle to ~8W with the i7 was a large part of my intention, and I'm not inclined to give any of those gains back.
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Without the fresh thermal paste job, the machine would have been running with the fan at max speed, CPU temp at 99degC, and serious throttling- with the
screensaver. Good grief.