All my tests on V1 IO.
CPU cooling is big stock heatsink plus extremely small fan blowing parallel to the heatsink.
For these tests, no "software cooling" was used.
For these tests, no measures were taken to cool Q16. (Highly inadvisable!)
For all K6-III tests, VCore = ~1.90-1.93V.
On a WinChip-200, this results in a CPU-temperature drop of about 5-6C. I suspect the numbers for Q16 did *not* drop as much compared to the CPU readings; the fan in my unit blows nothing towards Q16.
V1 sensors are: CPU (beneath CPU), mobo (near a capacitor near Q16), no third sensor.
WinChip 200: 45-50C on both sensors. 52ish without fan. 45ish with fan.
Tests with the case assembled (RF shield in place, backshell in place) for real-world temperatures:
K6-III-166, 2.5x66, 45C CPU, 61C mobo.
K6-III-200, 3.0x66, 48C CPU, 64C mobo.
K6-III-300, 4.5x66, 55C CPU, 80C mobo.
At 80C on Q16 and an hour of torture, I aborted the test. There was a slight discoloration (read: start of a *burn* mark) around Q16 after the test.
Tests with the case "open" - lots of free-flowing air around everything - for reference only - this is an exposed motherboard, not terribly useful for real-world use:
K6-III-300, 4.5x66, 38C CPU, 61C mobo
K6-III-285, 3.0x95, 38C CPU, 62C mobo
K6-III-266, 4.0x66, 36C CPU, 56C mobo
K6-III-250, 2.5x100, 36C CPU, 56C mobo
Airflow around the heatsink is clearly critical to proper cooling of both CPU and Q16. Closing up the box gave me a 17C increase in CPU temperature, and a 20C increase in Q16 temperature when running at 300 MHz.
Probably worse than that, since the "mobo" sensor isn't measuring the temperature of Q16, but of a component about half an inch away.
Finally, again, my "CPU" temperatures are probably at least 5 degrees cooler than temperatures from a passive heatsink because of my small fan.
You should be able to easily beat my "CPU" temperatures by using a Lasagna or equivalent fan directly on the CPU.
You should be able to easily beat my "mobo" temperatures by using thermal epoxy and a heatsink on Q16, and/or thermal epoxy, a heatsink, and a very small fan on Q16.