Post
by mark314 » Fri Nov 19, 2010 2:16 pm
DO NOT DO THAT.
Let's look at this. There are 2 specifications that are important. The maximum temperature of the CPU (Tcase) and the wattage of the system at full load (TDP). Intel recommends that the CPU be kept beneath Tcase for long term stability.
The Atom 330 has an 8W TDP and a Tc of 85.2C. In comparison, the E8400 has a 65W TDP and a 72.4C Tcase. The E8400 is the middle of it's class, and TDP is rated by class. Let's say real life TDP for the E8400 is 50W.
Let's say HFX engineered their solution to provide dissipation of the required 8W. Assuming an ambient temperature of 30C, that means their heat pipe system is designed to dissipate 8W with a temperature increase of no more than 55.2C. Their cooling system has a property called thermal resistance, which is basically a measure of the system's ability to dissipate heat. The lower the resistance, the more power can be dissipated with a given increase in temperature.
When they designed their system, they calculated the thermal resistance required to dissipate those 8 W over no more than 55.2C. The resistance R is basically 55.2 / 8 = 6.9.
So they have designed their cooling system have a measured thermal resistance of no more than 6.9. Hopefully they gave themselves some leeway, so let's assume they assembled a heatsink that had a resistance of 5. The resistance of the system is the sum of its parts, but generally speaking the heatpipes have negligible resistance.
Now let's look at how your new CPU will fare when you use their cooling system.
Thermal resistance, R = deltaT/Q, which rearranged is deltaT = R*Q. Q is the TDP of the system. R is 5. 5*50 gives a deltaT of 250, which added to the ambient gives your CPU a Tcase of 280C at full load. Barbeque time! In fact, your E8400 would need a heatsink with an R of (72.4-30)/50, or 0.85. At absolute max. I've researched this extensively and I can tell you that to get a heatsink with an R-value in a form factor that size, to operate completely passively is very hard and very expensive.
Now, maybe the resistance of their system is lower than 5. Maybe it's a lot lower - maybe it's even R=1 (not likely). Even so, remember where I said the heatpipes have negligible effect? That's assuming they adhere to the manufacturer's specifications. Those pipes look like they are 8mm. Generally, specifications on the heatpipes say to keep bends to a minimum, and to keep each bend to a bend radius of no more than 1.5 times the diameter of the pipe. In this case, a bend radius of just under 0.5 inches. Look at those pictures. Those pipes are bent so far that they are buckling. Every normal high-radius bend translates to about 3C temperature loss. I can't even speculate how much is lost on those tight bends. There will be serious loss of performance in those pipes, exacerbated by you if you have to bend them further to match them to your new motherboard.
Moral of the story - save your hardware, don't even try it!
Edit: I should point out that those calculations are for a theoretical maximum. The TDP of a CPU can only be reached with benchmarks - real use maximum power might only be 30W or less. Still - even 30W requires a heatsink with an R of no more than 1.4. That 30W for you still translates to a slightly cooler barbeque of 180C.
