Again, I am not saying you lie, but just may be we are in the wrong direction. Re-paste seems doing nothing actually (assume NB is not the root cause), however, if you did reseat the CPU / RAM etc during the re-paste process, that may be the action that actually fix the problem (re-seat CPU sometimes did the tricks).
All we can tell at this moment is you fix 2 crash by the "re-paste process", but cannot conclude that it's actually the NB cause the trouble. Do you know what I mean? We simply don't have enough data to conclude that. Especially the NB temperature and the NB heatsink temperature both looks rational.
If the thermal paste is not working at all. With that 25xx RPM, I will expect the heatsink is much cooler than the NB chip (because all heat are trapped inside the chip but cannot transfer to the heatsink effectively). Also, the NB can reach 100C (or over).
I never touch my NB (my Mac works fine, I don't want to over do the maintenance and kill it), but I Am really interested in the difference before and after the re-paste. Could you mind share the temperature that's after the re-paste? And for better comparison, that's better also under 100% stress with system ambient around 31C.
And which solution you use to replace the original rivet?
Just some sharing.
I have a 7950 and a R9 280 inside my 4,1. The R9 280 shows some artifact occationally about 2 months ago (randomly a small block of square on the screen in different colour). That's looks like a graphic card failure.
And what I did is pull out the card, blow the dust from the exhaust (pushing them backward), blow the slot. And reinstall the card.
After this process, no more artifact for more than a month now. Can I conclude that I blow the slot fix the issue? Or I blow the card fix the issue? I cannot, in fact, I re-seat the card as well, and also including a unintentional SMC reset. All these may contribute to the fix, but I don't know which part is the key.
The card never shows overheat, it never works above 70C, however, this "blowing out the dust from the card" process fix the issue. I can only say this process fix the issue, but not any particular part of the process fix the issue.
To others, I remember that when I bought my HIS IceQ R9 280 last year. Someone said HIS card usually is a trouble maker. I am happy to say that so far I only has 2 problems.
1) the artifact mentioned in above. And that's fixed. I suspected that when I opened the case and take out the PSU for cleaning few months ago (really dusty after almost 7 years of 24/7 usage in a higher air polluted city), I actually leave some dust in the slot, and that cause the occational artifact. Of course, may be the dust inside the card really affect some electronics. I can't find out the actually cause, but anyway that's completely fixed now.
2) despite it has the standard port layout. If I boot from the Mac EFI ROM (either only the 7950 Mac Edition with EFI or the R9 280 also boot from the EFI ROM), the HDMI port on the R9 280 won't work (but if both card boot from PC BIOS, then the HDMI port is fine). That's no big deal for me. I have 2 cards and plenty of port. Also, all I need to do is just flip the switch. In fact, now I connect my TV to that port, and intentionally boot with EFI enabled to disable that port when I don't need the TV. Because even though the TV is off, OSX still consider the screen is there, sometimes my mouse cursor will move to that offed screen which is not very handy. And now I can control it via a switch, but no need to touch the cables (I know I can use software to disable the screen, but that's not a good solution for me, because the setting will be reset after profiles switching, and I switch between profiles multiple times a day).