Right.
What it comes down to, is this: can we reproduce the heatload from a processor, without using two TIM joints. (no Bill, I'm not in la la land, read it again).
IF, *for example* I use the 12 by 13 mm die, I'm already off a little bit in perfectly replicating either a P4 or an Opteron/Athlon FX, because the dimensions don't match perfectly.
Then the heatload is going to be distributed differently from the die than with the actual processors, further putting me out.
But the IHS is still going to transfer the full heatload through an area that's almost identical to the size of the core, albeit a little bit larger, because the IHS is pretty thin: it's more of a protection to prevent core crushing, than an actual heat spreader.
So...
by doing away with the second TIM joint, it reduces a significant variable in my setup, and I'm still reproducing a CPU heatload reasonably well, plus it's a bit easier to reproduce: TIM joint can be somewhat subjective.
So I can them measure the block's performance without having to figure out two TIM joint variability. (Well, actually, I still have to figure it out, but it's simpler).
The result is that you know how well you can expect a block to perform, because you'll have a C/W figure that you should be able to use.
The real question is: how am I going to take the temperature measurement, in order to get an accurate reading? The second TIM joint would normally add a few degrees.
AMD specs for measuring the temp within a heatsink, call for a 1.5mm diameter hole, whose center is 2.2 mm from the base. The heat die is going to be different, but how?
BTW, AMD specs now call for a thermocouple to be mounted directly on the IHS, and the HSF to be notched to give room for it.
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