10-01-2007, 02:08 AM

Quick technical question about the heatsink in the MBP (I'm formulating a theory for the review I'm in the process of getting around to getting ready to get around to writing... *rolls eyes*)

It looks to me, from the literature that I've read, like there is no real-for lack of a better term-direct mechanical connection between the board and the heatsink. That is, as I understand it, the heatsink is attached to the bottom case, and the board essentially rests on top of it. There are no springs, no bolts, no clips, nothing that put pressure on the joint between the chips and the heatsink, correct?

Or am I mistaken?

Thanks.

10-02-2007, 01:28 AM

Well sure there is. The screws holding the logic board down are applying pressure. These screws are threaded through holes in the frame on the bottom case.

10-02-2007, 04:00 AM

Essentially, the heatsink is screwed onto the motherboard (technically, the motherboard is screwed to it, since the MB is on top). However, this DOESN'T mean there is even, strong pressure on the chips. On desktops, there is very clear, obvious pressure you can see and feel on the chip itself while attaching the heatsink. But on the MBP, we can only assume the heatsink itself is slightly higher than the threaded screw holes, therefore guaranteeing some sort of pressure against it as the screws are tightened. But once those screws bottom out, should something warp and cause the contact area of the heatsink to drop even the slightest amount, there's nothing you can do to bring it closer.

I'm finding it particularly hard to describe what I mean - I hope people reading this will understand.

10-04-2007, 03:24 AM

Thanks to both of you! That's what I wanted to know. I tracked down a high res pic of the board and looked more carefully at the heatsink. I have a feeling that this mounting system explains quite a bit.

10-04-2007, 09:17 AM

But with the amount of thermal grease they use from the factory, the contact is most likly not the greatest. When i open mine up to replace the dead fan i will also prob remove the old thermal grease and apply much less.

10-04-2007, 11:34 AM

I'm thinking that the excessive thermal grease is a contributing factor but not necessarily the root cause of the issue.

10-04-2007, 11:44 AM

Check my post on it with pics, too much is def a bad thing. And, well how much apple uses "too much" in an understatement. Check peoples post who re-applied with arctic silver, huge drops.

10-04-2007, 12:46 PM

I never said that the thermal compound wasn't a problem. It is. All the evidence out there is, as you said, indicative of the fact that it is a problem.

However, thermal compound costs money, and Apple's accounting department is not likely to be pleased with spending money unless there's a need for it (and don't think they wouldn't argue over $0.05 per machine or whatever... accountants at big companies will do that sometimes). Apple's engineers are not stupid, either. They may have their hands tied behind their back sometimes, but they're not stupid. What I'm saying is that they wouldn't do what they're doing unless they had a reason for doing it. I've got a good idea of what the reason is, and imo, it's not a good one, but I do think they have a reason. Not everyone that's reapplied with AS5 has reported temperature drops. The vast majority of people have, but not everyone has. I'll elaborate on my theory later, but I think I know exactly why Apple is applying as much thermal compound as they are, and while excessive thermal compound is a bad solution to the problem, I don't think it's an accident or unintentional.