Review: SilentTEK - AOpen's mobo-embedded fan controller

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While there are many different ways of setting up the SilentBIOS/TEK system, most readers will be interested in typical applications. Besides, detailing the various options would be far too tedious. Some operational basics:

1.: Most users will simply set the fan speeds in SilentBIOS to 50% for BOOT and OS.

2. When Windows is launched, the fan speeds will thus be at ~6.4V for the CPU HSF and ~5.25V for the system fan.

3. In Windows, whenever Fan Speed Control is enabled in HM III / SilentTEK, the SilentBIOS settings are superseded by the selected Fan Speed Control mode. This occurs automatically if HM III / SilentTEK is set to turn on with Windows.

4. Exiting SilentTEK reverts fan control to 100% manual, and all fans are fed 12V until SilentTEK is turned on again or the system is rebooted. This behavior is a kind of fail-safe to ensure the system does not get overheated if SilentTEK is turned off accidentally.

5. Engaging changes in settings sometimes seems to require hitting the SAVE button. At other times, it is enough to simply click on OK. A bit of trial-and-error may be in order.

6. The default behavior of the SilentTEK interface is to shut the program down completely if you hit EXIT or X. This is not well thought out. A background control program like this one should have a two-stage shutdown whereby EXIT closes the interface but does not turn the program off. Clicking on a taskbar icon (that always stays on when the program is on) should provides options to bring the main interface back or shut the program down. This is the behavior of programs such as Motherboard Monitor, which runs in the background much like SilentTEK.

Whatever fan control mode and settings are chosen, it is necessary to ensure that the heatsink fan has to adequate cooling power for the CPU. In other words, SilentTek does not eliminate your responsibility to ensure adequate cooling under whatever super-quiet fan mode you choose.

For the Intel P4-1.8A test system mentioned earlier, several different heatsinks and fans were tried:

  • Thermalright AX478 HS
  • Zalman 6500B-CU HS (large flower)
  • Zalman 5700D-CU HS (radial flower)
  • Panaflo FBA08A12L1A 80mm fan
  • Zalman 80mm fan

Any of the above HS have the capacity to keep the P4-1.8A at under 50C (while stressed 100% long-term) with fan running at 7V steady. This is with a room ambient temperature of 20C.

The P4-1.8A was also run overclocked to 2.4G (133 MHz bus) with a Vcore of 1.625V. It is difficult to calculate exactly how much power the CPU generates at these settings. Given that a stock P4-2.4G at 1.5V is rated for a maximum of 59.8W, 65W is probably a reasonable guesstimate. This compares with ~50W maximum for the P4-1.8A at stock speed and voltage.

1. Smart Fan Control

CPU set to 50C, SYS set to 40: In normal PC usage, with web browsing, email, some Office apps, Photoshop, etc, the CPU fan almost never came on. Typical CPU temperature at 1.8G ranged 31~37C, and rose to 35~43C at the overclocked setting. The fan connected to SYSFan2 came on periodically without any apparent reason, usually at minimal voltage.

CPU Stress testing pushed the temps to 50C and 40C in 5 minutes, and turned both the CPU and SYS fan on, usually at 51C and 41C. The fan voltage ranged 6.4-10.5V when. The fans would stay on for typically under 1 minute, during which time the temp would drop by a couple of degrees, then they would turn off. This went on in a continuous cycle. The CPU temp never went past 53C.

In many ways, this is a perfect fan control mode for most users: Minimum effort, excellent control.

2. Fix Fan Control

There's not really much to discuss here. As described in the section above, this feature is a manual fan speed controller with 12 discrete positions. 6.4V is a bit high for minimum voltage with some fans, but it is good enough with most quiet fans. It is the ideal fan mode for those who never want to hear changes in noise level.

3. Multiple Fan Control

There are many ways to set this up; only one will be described here -- Example B. Higher temp version of Quiet but Safe from the previous section on page 2.


The fans never came on with either the stock or overclocked CPU settings in normal use. When stressed 100%, the CPU temp reached 60C in under 10 minutes. At either settings, the CPU temperature was held to below 65C with all HS and fan combination at the reasonably quiet 7.75V level. The fan stayed on continuously at the oc'd setting; it turned off from time to time at the stock setting.

It's more effort than any of the other modes, but fun to play with, although whether it actually provides superior performance really depends on your specific goals and the level of your understanding of noise, cooling, psychoacoustics, etc. Not recommended for the casual users but possibly rewarding for sophisticated geeks.

4. AOpen Recommend Setting

We know this is basically a customized version of Multiple Fan Control. The commentary here is for only one HSF: Thermalright AX478 with Zalman 80mm fan.

The fan rarely turned on in normal use with either stock or overclocked CPU settings. Under stress, the fan turned on around 46C. Interestingly, the startup voltage to the CPU fan in this mode was 4.5V, much lower than the 6.4V available in other modes. With the stock CPU settings, the fan voltage climbed to 7.7V and stabilized there, holding the temp to 51C. With the overclocked settings, the fan voltage again reached 7.7V, and held the temp to 55C.

To find out whether there are any significant changes in the fan control algorithm when used with a different CPU, a P4-2.8G was pressed into service, using all default settings. The AOpen Recommend algorithm did not work consistently with this CPU, however. Depending on the sequence in which the AOpen Recommend was engaged, it would start the fan as low as at 35C and not spin down even at 31C. Other times, the fan would not start even well beyond 60C. I can only conclude that the AOpen Recommend does not recognize the P4-2.8 properly.

So with the P4-1.8A, the AOpen Recommend setting works well to keep the CPU cool with hardly any noise in normal use, perhaps as well as or better than any other setting, due to the low 4.5V fan start voltage. This means a higher airflow fan can be used to provide improved cooling while keeping noise inaudible. The AOpen Recommend setting with the P4-2.8 tried was inconsistent, so is not a good option. I'd recommend some experimentation with your CPU before choosing AOpen Recommend as your default setting.


AOpen's SilentBIOS/TEK is by no means a flawless execution of an embedded thermal fan control system in a motherboard, but it is the first serious attempt. An ambitious, flexible and powerful software utility, its inclusion of the CPU temperature diode data into a fan control feedback loop gives it a great deal of power and accuracy. Some peculiarities, ambiguities and idocyncracies have been noted, but in my opinion, they are not serious enough flaws to offset the many noise / thermal control benefits provided.

This is not the first implementation of a software fan controller that uses motherboard embedded resources. Listed in