Foxconn better than SCV GC68

[mechBgon]

I own both a GC-68 and an Alpha PAL8045 (yes, and an A7V333 too). I can't imagine anyone holding these two heatsinks in their hands and imagining that the GC-68 approaches the cooling capabilities of the 8045.

 

[Jhhnn]

Not even in your wildest dreams, Mikewarrior2. Heat output is measured in btu/hr, calories/minute, watts/ any length of time you'd care to choose. Time being the part you're forgetting. If the cpu is putting out the same amount of heat over a given period of time, regardless of the hsf employed, then where would that heat go, other than out the case exhaust? The actual amount of heat dissipated must be the same, otherwise the cpu temp would continue to rise until it fried. The reason that the heat dissipation remains the same is because the temperature differential between the cpu and the air increases with the lesser hsf until a point is reached where that difference allows sufficient heat transfer to achieve equilibrium.

Think of it like this- two buckets, one taller than the other. Run water continuously (heat) into both of them at the same rate, let it overflow over the tops(case exhaust fan). Measure the height of the water in the buckets(cpu temp). Even though the height of the water is different, the flow rate is the same. HVAC 101.

 

[OulOat]

Originally posted by: Jhhnn
Not even in your wildest dreams, Mikewarrior2. Heat output is measured in btu/hr, calories/minute, watts/ any length of time you'd care to choose. Time being the part you're forgetting. If the cpu is putting out the same amount of heat over a given period of time, regardless of the hsf employed, then where would that heat go, other than out the case exhaust? The actual amount of heat dissipated must be the same, otherwise the cpu temp would continue to rise until it fried. The reason that the heat dissipation remains the same is because the temperature differential between the cpu and the air increases with the lesser hsf until a point is reached where that difference allows sufficient heat transfer to achieve equilibrium.

Think of it like this- two buckets, one taller than the other. Run water continuously (heat) into both of them at the same rate, let it overflow over the tops(case exhaust fan). Measure the height of the water in the buckets(cpu temp). Even though the height of the water is different, the flow rate is the same. HVAC 101.

So you are saying that I can use a Pentium heatsink on a P4, since there will be a point where the P HSF would dissipate the same amount of heat as a P4 HSF

You are absolutely right about the heat dissipation. But you forgot to consider one thing. The only reason a sh@tter hsf would dissipated the same amount of heat as a good hsf would be because the heat buildup on the CPU would be far greater. Using your analogy of the buckets, let's assume we have 2 buckets of the same size (representing the CPU). We make a hole on the side of each bucket, one larger than the other to represent a better hsf. Then we add water (heat). As you can probably guess, the larger hole would start leaking more water than the smaller hole. But, as you keep filling both buckets with the same amount of water, you would notice that as the water level rise faster in the bucket with the smaller hole, that bucket would start leaking water at a faster rate. There would be a point (equilibrium) in which both buckets would be leaking water at the same amount as water is being added, but the volume left in the buckets would not match (in fact, the bucket with the small hole would have to have more water in it than the one with the larger hole). Also, note that if the bucket ever overflows, then that would mean the CPU is fried (too much water for the bucket to handle). Thus, the bigger the hole one bucket has compared to the other, the less water there would be in the bucket and the less chance of water overflowing the bucket.

Bringing this back the CPUs, better HSF would allow the CPU to retain less heat, while a lesser off HSF would require the CPU to reach a higher temp before dissipating the same amount of heat.

 

[Jhhnn]

OalOat-

Your last sentence is correct.....

 

[Mikewarrior2]

Jhhnn,

NO, irregardless of time involved, you're wrong.

In order for equilibrium to be achieved, you'd need a closed system. Last time I checked, a comptuer case is nowhere near being a closed system.

Secondly, your bucket analogy makes no sense.

Thirdly, if the CPU is running hotter, then obviously it isn't dissapating heat into the heatsink. It is retaining heat. Less heat for the overall system, therefore less system case exhaust temp.

Explain how a CPU that is hotter is contributing the same amount of heat to a case as one that is running cooler, despite producing the same amount of heat.


Mike

P.S. Instead of your bucket comparison, let's your a car engine /radiator comparison.

Let's just say hte engine produces 100W of heat. Radiator A is a very good radiator, and the engine is running at a theoretical temp of X.

Lets take the same engine and pair if with radiator B. Radiator B is not as good a radiator, therefore the engine is running hotter, due to "retaining" more heat with radiator b than it does with A. Since there is less heat transfer occuring, Radiator B will appear to run "cooler". Radiator B is less effective, which is hwy the engine is hotter. In this "pseudo" closed system, conservation of energy would exist since the engine is running hotter, and hte radiator "cooler".

 

[Mikewarrior2]

I am no longer going to reply to htis thread. It appears i have angered those who think the $6 GC68 to be teh equal of a well engineered HSF like an Alpha.



mike

 

[Lucky]

i dont know who to believe here.

 

[nemo160]

mikewarrior2 knows his stuff

 

[drx9175l]

Forget all the analogoies and forget the physics lessons. Mikewarrior2, please explain how the GC68, or any HSF, could possibly "trick" the thermal sensor into reading an lower temp? Agreed that the sensor isn't perfectly accurate and that temps. will vary wildly between motherboards. But, in a system where only the heatsink is changed (keeping the same fan, just for consistancy) why would the temp. readings drop? You state that the heat must go somewhere. With the GC68, if more heat is being kept on/in the CPU, why wouldn't the sensor report the increase?

BTW, I don't own the GC68. I have an Alpha 6035.

 

[Nerdwannabe]

Allow me to jump into the topic.

1st, thermistor is no way accurate. It can be off as much as 15%.
2nd, when you change the heatsink, you are also unloading and loading the cpu. This will change the position of the thermistor.

If you really want to compare the heatsink performance, please get 2 good thermalcouples, one touch the cpu die (cpu temp), the other one place just above the cpu intake fan (cpu ambient)

You will compare the result (cpu temp) - (cpu ambient) between 2 heatsinks. The smaller number gives you the better heatsink.

ps, the cpu temp you get is still not the accurate cpu die temp, but at least it will be more consistant and closer to actual die temp.

 

[keyeye]

I believe Jhhnn is correct (though I'm no heatsink physicist). The CPU produces a fixed amount of heat per unit time irrespective of the heatsink attached. The amount of heat transferred from the heatsink is dependent on the temperature differential between the intake air and the heatsink (i.e. greater temperature difference is greater heat transfer (in general)). Thus, an inefficient heatsink can still offload the same amount of heat (per unit time) as an efficient heatsink, but will require a much higher temperature differential (e.g. higher heatsink temp and therefore CPU temp) to overcome the inefficiency. I believe this is reflected in the C/W ratings of heatsink fans (though I never believe them between manufactures). A more efficient heatsink requires less rise in temp (C) to offload a given constant heat output (W).

I don't think Mikewarrior's analogy makes sense. The engine radiator system is ok if you only inject at one time 100W worth of energy. Then, conservation of energy results in the engine being hotter than the radiator. However, most engines continue to get gas and thus generate more heat. If the engine cannot get rid of the heat, the temperature will continue to rise ...