Heatsink / Fan Head-to-Head
by Len "Viking1" HjalmarsonArticle Type: Hardware
Article Date: March 19, 2002
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Crank up the Heat!
Combat flight simulation fans tend to push their systems to the limits. For many of us, that includes overclocking components like CPUs and video hardware.These components, however, tend to generate a great deal of heat, and are already running near their limits. The only reliable way to overclock the last generation of Pentium 4 chips or the current Athlon chips is to increase the cooling efficiency. This is why there is a strong market for high-powered, high efficiency heatsink/fan (HSF) combos.
Up to recently, I was content with the clip HSF combination for my Athlon XP. After reading the reviews, I made the switch to the Alpha PAL 8045. Not long afterward I noticed that the Swiftech unit was performing even better. Coolerguys.com graciously provided me with a unit for testing, and this review details those results. Let’s begin with the Alpha PAL 8045.
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| Alpha PAL 8045 |
Alpha PAL 8045
Test System:
- DFI AD70-SC mainboard with Athlon XP 1900
- 512 MB Corsair DDRAM
- WindTunnel II Gamer ATX Case
- Nvidia GeForce 3
- Creative Audigy
- LiteOn CD R/W
- IBM Deskstar 40GB
The Alpha PAL 8045 (AP8 hereafter) is not a completely copper heatsink. Instead, this unit has copper imbedded in the heatsink so that the contact point to the CPU is copper.
The unit itself is heavy and impressive. It consists of the solid base and 864 hexagonal fins (!). It comes stock with an 80mm fan, and the unit is the same size. Consider for a moment that his is almost double the area of a 60mm HSF. For that reason, and because of the weight, you can’t simply open up your system and clip this unit onto your CPU. Instead, you have to remove your motherboard and use a special mounting system developed by Alpha.
The AP8 comes complete with screws, washers, nuts and springs to mount the unit. The screws are metal and the washers are nylon. Mounting itself is a simple process and does not require a mechanical genius. Clear instructions are provided in the form of a double-sided instruction sheet.
Installation is in four steps. First, four threaded grommets are mounted to the base of the mainboard, and secured by nylon washers on the underside of the mainboard. All current mainboards have holes surrounding the CPU socket to allow the mounting.
Next, the CPU is inserted into the socket and the thermal transfer paste is applied. (In many cases you will want to apply the thermal paste before you insert the CPU into the socket). Once the CPU is secure, the heatsink unit is positioned over the CPU and mounting grommets.
Finally, the screws (with springs applied) are inserted into the mounting holes on the heatsink and tightened until they hit bottom. It is almost impossible to overtighten the screws, and very easy to tell when they hit bottom. The springs supply the pre-calibrated tension. At this stage you can add a fan or not. The heatsink itself is so efficient you can actually use it in a well ventilated case without a fan. Naturally, a fan increases efficiency.
Once you’ve done the installation you can remove the unit later without having to remove the mainboard again. If you upgrade your CPU you should not have to remove the mainboard in order to make the switch.
The fact that you must remove your motherboard isn’t a deterrent to those building a new system. It’s really a very simple process, and installing the Alpha took me about ten minutes once I had removed my mainboard. But for others who may never have installed a mainboard, I suggest you stick with a spring clip type unit.
There are two electrical connections to the fan supplied. Since these large fans draw a great deal of power (4 W), most mainboards will not make the grade and the user risks burning out a circuit. For this reason there is a 12 volt connector that will go straight to your power supply, and an additional connector for the mainboard to monitor fan RPM.
When I first tested the AP8 I tested with a 53 CFM Mechatronics fan. The Mechatronics is a great deal quieter than the more powerful Delta 68 CFM fan, yet the temperature under load with the Mechatronics was almost the same as with the OCZ Gladiator running the more powerful Delta, only .6 C higher.
SWF 462
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| SWF 462 |
The 462 is another huge HSF combination, and like the Alpha PAL it requires removal of the mainboard to mount the unit. Like the Alpha PAL, the unit mounts to the mainboard on a set of four threaded grommets, and then the HSF is screwed to the grommets with four screws passing through four springs.
The structure of the unit is also similar. There are fewer fins (closer to 370), and the base of the unit is solid copper. The entire heatsink weights about 560 grams.
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| SWF 462...lots of fins |
The actual size of the heatsink is almost identical to the Alpha PAL. This is likely because you can’t really mount anything larger than the 3” by 3” of these units.
Following the same process as the Alpha PAL I mounted the anchors to my mainboard, inserted the CPU, and then mounted the unit, driving the screws against the springs until they hit bottom. I used the same Arctic Silver III thermal paste for both tests.
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| View of the mounting system |
I connected the 12 volt lead directly to my power supply, and then connected the fan monitor lead to my mainboard. All tests were run with the system overclocked to 1713 MHz.
My first trials were at default voltage of 1.75. On the AP 8045 CPU temperature in WIN ME at idle in my moderately cool office (16C) was 27C. At the maximum overclock where the system would run stable the temperature hit 34C.
| CPU (MHz) | FSB (MHz) | Voltage | Temp |
| 1600 | 133 | 1.75 | 28 |
| 1684 | 140 | 1.75 | 32 |
| 1753 | 146 | 1.75 | FAIL |
| 1753 | 146 | 1.80 | 34 |
Repeating the tests with the SWF 462 the chart looked like this..
| CPU (MHz) | FSB (MHz) | Voltage | Temp |
| 1600 | 133 | 1.75 | 28 |
| 1684 | 140 | 1.75 | 32 |
| 1753 | 146 | 1.75 | FAIL |
| 1753 | 146 | 1.80 | 33 |
| 1777 | 148 | 1.825 | 34 |
| 1800 | 150 | 1.85 | 35 |
I have never had my system run stable beyond the 1753 mark, so it was encouraging to see the improvement with a more efficient HSF combination.
Notes on Thermal Grease
Only recently I went from the original Arctic Silver thermal paste to AS III. I had read that the latest improvements in thermal efficiency were arriving as a result of new polysynthetics combined with pure silver. AS III is almost 99 percent pure silver, and its thermal conductivity is rated at 8.0 W/m*K. (One tube will do about eight CPUs and costs about $10 US).  |
| Incomparable Arctic Silver III |
Thermal grease is that thin layer of grease that is applied on top of the CPU prior to installing an HSF. It compensates for any irregularity in the contact surface, and it facilitates the transfer of heat between the CPU and HSF.
Thermal grease is thermal grease, right? Not necessarily.
Conductive grease varies in efficiency about as much as the HSFs you can purchase. Furthermore, the incorrect application of thermal grease will limit the effectiveness of heat transfer between your HSF and the CPU.
The first grease I used on my Alpha PAL was a stock item available through Radio Shack. It is white and probably lithium based. It spreads easily and is rather nice to use.
I spread a thin layer on top of my CPU using a flexible plastic spreader. I then placed the HSF on the CPU and removed it again. I could see that the entire area was dimpled, a good indication that the grease was making contact across the entire area.
I tested the CPU under load and achieved an operating temperature of 32C at 1466 MHz with VIA s hardware monitor. At 1753 MHz, however, the temperature soared to 51C. I then shut down the system, removed the HSF, and cleaned all the grease from the HSF and CPU
Next I applied the original Arctic Silver from a small tube. This stuff is a bit of a pain to work with, since it is quite thick. It helps if the tube and CPU are slightly warm.
It’s impossible to apply this paste with a finger tip, and it is not a good idea to do so, since the oil on your fingers is not as efficient at thermal transfer and can even reduce the efficiency. The best way to apply the compound is to use a stiff plastic like a credit card.
I reset my HSF in place and closed the system down. I ran my system overclocked at 1753 MHz under load for twenty minutes and checked CPU temperature with the VIA hardware monitor. The indicated temperature was 49C.
It’s difficult to know for certain whether the difference is incidental, so I ran the test a second time and achieved a temperature of 48C. I then removed the HSF and cleared off the Arctic Silver, and applied the Arctic Silver III. I ran the system for 20 minutes under load and achieved a reading of 46C. It does seem that an improvement in heat transfer is achieved when using the latest thermal paste.
Conclusion
The average computer user will be well content to run his or her system at default speeds and achieve reasonable performance. The flight simulation fan, particularly those of us who build our own systems, are rarely content with average performance.Running video hardware and CPUs beyond rated speeds is risky if you don’t know what you are doing, and is not likely to result in a stable system unless you have a high efficiency HSF. It looks like either the Alpha PAL 8045 or the SWF 462 are good choices.
But the best air cooler on the market right now appears to be the SWF 462. Used in conjunction with the latest thermal transfer paste, you can’t do any better. I highly recommend either of these coolers and Arctic Silver III.
Cooling Resources
Articles- 2001/10/24: Cooling Part I
- 2001/10/25: Cooling Part II
- 2002/03/19: Heatsink / Fan Cooling
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