Linked by Thom Holwerda on Tue 11th Jun 2013 17:07 UTC
Apple We already talked about iOS 7 yesterday (after a night of sleep, it's only looking worse and worse - look at this, for Fiona's sake!), so now it's time to talk about the downright stunning and belly flutters-inducing new Mac Pro. As former owner and huge, huge, huge fan of the PowerMac G4 Cube - I haven't been this excited about an Apple product since, well, I would say the iMac G4. This is the Apple I used to love.
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RE: ... and as usual
by galvanash on Thu 13th Jun 2013 06:36 UTC in reply to "... and as usual"
galvanash
Member since:
2006-01-25

They have the cojones to brag about sharing an ALUMINUM heatsink with everything? REALLY?!?


I have to disagree with you on this one... Yes, copper is a better conductor of heat, and in any steady state setup (where the amount of heat is constant) a copper heat sink will outperform an aluminum one of the same size and design (assuming it is machined and not soldered).

But CPUs and GPUs don't work like that anymore... Yes, they used to more or less dissipate at a constant rate, but they do not anymore. The same argument that applies to Intel and AMD's "turbo" clock speeds applies to the argument for using aluminum (selectively) - what you are trying to do is hurry up and idle.

This argument (for CPUs) is to save power. By going fast in burst you reduce overall power usage because most of the time you don't need to go fast... So by sprinting in small bursts you end up reducing overall power use because you can keep the processor in an idle state (with reduced power requirements) faster.

The same argument applies to heat sink design, since power = heat. Aluminum has much less mass than copper - once the heat is removed it cools off faster. Copper is better because it can transfer heat faster, but it also retains that heat longer than aluminum does once the heat source is gone (because of its mass).

So if your thermal load jumps up and down a lot, and spends more time down than up, aluminum will tend to have more cooling capacity available when you cycle back to load (the junction differential will be higher). This is especially true if you are using some form of evaporative cooling (i.e. heat pipes), which this thing almost certainly is.

I would say that yes, under constant 100% load choosing an all copper heatsink would likely have been better for overall performance (i.e. higher constant clock speeds could be maintained). But if your goal is to dissipate as fast as possible when you hit idle, aluminum is better. If clock management on the CPU and GPU is tuned for such "hurry up and idle" behavior (and on modern machines it is), then such a design may well perform just as well if not better than copper most of the time.

Look at the current heatsink market for validation of this... There are a lot of very good aluminum + heat pipe designs out there.

ps. Seperating the heatsink makes even less sense from a thermodynamics point of view. What you want if you are trying to design the most efficient way to dissipate heat is treat the entire system as a single load and concentrate your efforts on removing the required amount of heat as quickly as possible, but no more. There is no benefit at all to having separate heatsinks, all it does is complicate the design needlessly.

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