Fanless (or Not) with TKPower 300 & VIA C3

Do-It-Yourself Systems | Power
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DUALING FANS

It was decided from the outset that this system would be built to run entirely fanless, but that fan options would be included in order to test their effects on system noise and system temperature. This picture above shows a Zalman fan bracket attached to 2 Panaflo fans. The top fan is positioned to blow on the CPU heatsink, the bottom fan is positioned to blow on the hard drive located on the floor of the case. Each of these fans is attached to a Zalman FanMate resistor device, and each will run at the lowest voltage which the FanMate would provide and essentially the lowest voltage at which the fans would start. Fan voltage could be controlled with the FanMates, which were positioned outside the back of the case. In addition, the power supply for each fan could be switched on or off from outside the case, allowing instant assessment of the contribution of each (and both) fans to system noise and system temperature.

This picture shows the Barracuda IV suspended in its mounting frame on the floor of the case (red arrow). 6-point attachment makes significant displacement of the hard drive very unlikely. The frame is fixed to the floor of the case with 4 mounting bolts.

MEASURING TEMPS

Near the top center of the case, the white Radio Shack thermometer which measures case air temperature is seen just above the RAM sticks. The thin black wire just left of that thermometer is the Compunurse thermometer that is placed between the heat sink and the cpu. (Note: That thermometer is not on the heat spreader. That placement would wreck the thermometer and possibly the cpu. The probe sits in the gap between the heatsink and the heat spreader, and touches the edge of the heat spreader.)

The VIA C3 Ezra is specified for operation with CPU case temperatures in the range of 0°C to 70°C. VIA recommends external CPU case temperature be measured by attaching a thermocouple to the center of the VIA C3 package, as the heat produced by the processor is very localized so measuring the case anywhere else underestimates the case temperature. This requires drilling a hole through the base of the heatsink and epoxying a thermocouple so that it is positioned at the center of the CPU when the heatsink is mounted.

Whether my thermometer probe position is valid is open to question. This point is moot as I don't have a thermometer that uses the kind of thermocouple which would make a true core temperature reading possible. Suffice it to say that the temperatures I report may be a few degrees lower than would be obtained at the absolute center of the CPU. Still, virtually all reports of other measurement techniques seem to be 2-15°C too low compared with CompuNurse-type thermometer readings.

The rounded IDE cables are very nice, a great improvement since they are easy to position, much less vexing than ribbon cables. They also decrease clutter and probably aid air flow.

This picture shows the position of the 2 Panaflo fans (artifically highlighted and marked with red arrows) in their modified Zalman bracket. The upper fan blows on the CPU heat sink, the lower fan blows on the Barracuda IV hard drive. This is the configuration of the computer at the end of the project. The side panel was later put back on the case, returning it to nearly the same external appearance it had before any modification was done.

FAN CONTROLLER

This is the fan controller. It features an off-on switch for each fan. There is also a variable resistor for the hard drive fan. Since each fan is supplied with an out-of-the-case FanMate, there is no need to use the variable resistor, though. This controller sits on the top of the case, although I could put it on my desk or in any other convenient spot.

This is the schematic for the fan controller. It might have been clearer if I had made a circuit diagram, but this seemed to be the most widely accessible approach. My general approach to these projects is to plan for everything to go horribly wrong. So, I never work on components: I work on extension cabling, which is cheaply and easily replaced. All connections are made with hot-joint solder and covered with shrink tubing. (My local electronic parts store wants to give me a Platinum Card.)

PERFORMANCE and CONCLUSIONS

This set of CPU temperature observations was made with variation in CPU fan voltage, under varying CPU load. The 7.4 volt reading came from testing the FanMate on my workbench, with the resistance at maximum. [Mileage may vary.] The hard drive fan was left off at all times. The lesson here is pretty clear: Going fanless is a possibility with this system, but at high processor loads the CPU gets hot. The rated maximum temperature for this CPU is 70°C. In fact, during fanless drive partitioning and formatting, CPU temperature reached 73.8°C. Although the CPU showed no signs of strain, this heating is probably not a good idea.

Please remember that VIA said only that the CPU could run fanless. It was never said that the whole system could run fanless. Convective cooling in a mostly-closed box is not very efficient. Even a slight amount of air movement makes a substantial reduction in system temperature.

When the hard drive fan is also running, there is an additional 2-5°C drop in CPU temperature. Hard drive temperature also stays down nicely, being routinely less than 42°C.

The case air temperatures tell a very interesting story. It is doubtful that much air is moving through this case with the current fan positioning. What is probably happening is that the heat from components is being spread to the 1.5 cubic feet (35,000 cc) of air in the case. The cooling power of this volume of air is substantial, and the key goal in system cooling becomes elimination of tiny areas of air stagnation in regions of substantial heat generation. This is why the low-voltage Panaflo fans make a big difference.

It goes without saying that this analysis only holds for systems which are not generating much heat, and for environments in which room temperature is moderate.

This review is the first computing work that I have done on the system which is being described. During preparation of this piece tonight, room air temperature has been 23.3°C, CPU temperature 36.5°C, case air temperature 33.0°C and hard drive 39°C. Both Panaflo fans have been running, and they are inaudible from my chair. Absent the power-on light, I could not tell that this computer was running.

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