I did a lot of testing and had a lengthy reply written back addressing many points. Sadly yesterday downloading UT3Demo legitimate from a legitimate file site at the same time, it had a relatively new virus and has messed my system up quite badly upon extracting. Now fixed it but lost all my desktop files including my pictures and notes which I had uploaded and posted in my reply. I'm not happy.

I'm not going in any detail now but just giving my results in a while when I can.

Quote Originally Posted by rge View Post
If you do cut the groove, could you test with heatsink on and off. With heatsink off, use idle and slowly bring temp up, allowing to equilibrate and compare measured temp to distance from tjmax at 45, 40, 35, 30.
You can't slowly bring temp. up without a heatsink. It's not possible unless you have the environment temperature controlled very well at sub <0.7V <1.2GHz or if you're applying static loads to reach such temperature. Without a heatsink, temperature shoots up very fast above 10W TDP on an IC. Especially when you reach >80C, the temperature runs away. Hence any sub-$100 probe I've seen cannot even read, calculate and feedback the real-time IHS temp. before the system shuts down (THERMTRIP#). The delay is such that, they will end up reading temps. approximately easily 5-10C short of the real Tcase temp., depending on how quick the temperature shoots up (very quick).
Once heatsink in place and actively cooling Tcase, you will be measuring Tcase accurately, but a more significant gradient will exist from core to tcase, while cooling tcase and loading core.
Yep.