[Since87]

Originally posted by Les
The step if it occurs is at a Coolant temp of -4C(ish) and a CPU temp of 9(ish).

Yes, thanks for pointing that out. I'm totally swamped with work right now, and am not able to devote the time to keep up very well with this very interesting discussion.

Originally posted by Les

That appears to indicate there is little dropoff in leakage current near 9C when the CPU is running at 2V. (A significant change in leakage would result in a more curved line.) Perhaps similar testing at a voltage closer the Vcore spec would be more revealing.

I was going to suggest more testing along these lines, but using temperatures to guesstimate current draw is just too backasswards. Maybe it's worth using the THG method of measuring current. Even 10% accuracy current measurements would be better than guesses based on temperature.

Originally posted by Les
Harvard Thermal TAS (Thermal Analysis System) which I have, sells an add-on unit PC Trace - which I do not have
this permits a very accurate thermal modeling of the board in terms of heat inputs and dissipation
Since87 – it models with resistors so can also predict boardwide voltages, interesting stuff
I do not doubt that mobo mfgrs use this (in fact I know of several)

this 'variable' is why even a grothmeter will still fail to accurately characterize the heat load actually imparted to the cooling solution

Yes, a motherboard is such a fugly environment to try to determine anything with accuracy.

Pulling the Vcore voltage regulator off altogether and running a bench supply to the CPU would improve things. It gets a major heatsource off the board and makes measurement of CPU power consumption easier. That would be a pretty serious hack job though, and would require some research into the power supply start up requirements of the CPU/motherboard.

Then you'd want to provide the North Bridge with a TEC setup to maintain zero dT between the NB substrate and the mobo right 'below' it. (Ensuring 'all' NB heat flows through the TEC.)

Then thermal epoxy the back of the motherboard (in the region around the CPU) to a slab of copper.

Then...