MiniDisplay Port AFFECTS CPU THERMALS (obviously)
First off, i'd like to say a big thanks for the OP for posting this thread and because of his thread, I took apart my 2011 17" mbp to reapply the TIM. Secondly, I found a HUGE discrepancy in my thermal readings:
https://forums.macrumors.com/posts/12098419/
Initial tests indicated that my temperatures did not seem to idle below 50C even when idle. When running a stress test using prime95 using 8-8k FFT's for 20 minutes each, the temperatures were about 86C even hitting 91C before the fans kicked up to 5500rpm.
The big discrepancy for me was THAT I HAD THE MINIDISPLAYPORT OUTPUT to a 24" monitor along with using SwitchResX (to disable the 17" laptop LCD). The GPU used was the discrete GPU since it is used to output to external monitor.
With the external monitor setup, the idle temperatures floated from 51C - 56C EVEN WITH THE THERMAL PASTE REAPPLIED. This led me to conclude this entire process wasn't worth the effort.
I've had about 20 startup/shutdown cycles now. Initial tests show the CPU hitting 86C under full load but dropping back down to 51C-56C on idle REAL QUICK (under a minute at best). This proved that the TIM applied was indeed legit and working great.
This morning, I had to unplug the external monitor so I started up the laptop without anything on the displayport output side. The idle temperatures were about 31C-33C. I opened up safari and mail and did some daily work and temperatures floated around 41C for idle at most. This led me to test out the minidisplay port output and when I plugged in the external monitor thru the port, the temperatures jumped up to the 49-52C WHEN IDLE. Unplugging it caused it to drop back down to 41C. The discrete GPU was STILL BEING USED even without an external monitor connected to the display port. I made sure it wasn't a discrete vs. built in HDM3000 intel issue.
I am now quite certain there's something going on with the display port power usage. Perhaps the discrete GPU is working harder causing more CPU heat...but until you unplug the device from the port, you will see both GPU and CPU temps drop down to the low 40C. It's a huge thermal issue.
Too bad I did not get a chance to test out the laptop without an external monitor connected to the minidisplay port so I can check the temperatures BEFORE I applied the arctic silver 5 TIM. I will conclue now after only about 20 cycles, reapplying the paste indeed works fantastically. I must retract my earlier conclusions now because it was the external monitor connection that somehow raised all the CPU/GPU temperatures for whatever reason.
When full on 8-8k FFT loaded on the CPU, the temperature without an external monitor connected hit about 86C then the fans kicked up to 5500RPM lowering it back down to 78C! But then the fans will die back down to 4000RPM's which will float the CPU temps back up to around the 80C's. I will contest without a doubt now that the AS5 TIM really made a huge difference in allowing the heat from the CPU to reach the heatsinks and the fans can cool the heatsinks down causing CPU/GPU temps to drop significantly increasing laptop usage lifespan.