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

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SILENT BIOS

Selecting the menu entry Silent BIOS / HW Monitor in the Phonenix-Award BIOS setup utility brings us to the main setup screen for thermal / noise control in the BIOS. It is combined with the hardware monitor functions of the board.

Main SilentBIOS setup menu

1. CPU Warning Temp, the first item on the screen shown above, is an emergency throttle feature designed to save the CPU from imminent demise from overheating and sound an audible alert when the selected CPU temperature is reached. The screen above shows it disabled. The screen below shows the 7 temperature options in the sub-menu for this CPU throttling utility. Shutting down the works and turning on the sirens at 50C seems a bit premature, but the option is there for the cautious-minded. The last setting is a mildly risky 70C. It is hardly a risk for a P4 as its own built-in protections will kick in if necessary.

Before SilentBIOS can be fully comprehended, you must realize the following:

  • It has some unnecessary complications and internal contradictions. Also, there is no manual for either SilentBIOS or SilentTEK.
  • AOpen needed to address a special issue related to its Juke Box CD player feature. This is a CD player function embedded in many AOpen motherboards. It is launched at power-up without waiting for the OS to boot. The idea is that you can turn on your PC, insert an audio CD and begin hearing music with minimum delay, as if the PC was a normal CD player. They decided this mode required more extensive ways of handling fan noise. At least half of the menu items in the SilentBIOS setup screen relates to this requirement.

It took quite a while for me to come to these realizations, especially the latter concerning Juke Box. So, moving on...

2. Two fans can be controlled via the BIOS, the ones connected to the 3-pin fan output headers on the motherboard marked CPUFan1 and SYSFan2. There are two settings for each of these fans: the speed during boot, and the speed when the OS is powered up.

For most PC users, the latter settings CPUFan1 OS Speed and SYSFan2 OS Speed are really all that matter here. They determine the default speeds of the fans once your OS is running.

To set the fan speed, any number between 50% and 100% of maximum can be keyed in, as shown in the left screen below. The voltages available for the two fan headers are not quite the same. At any given percentage setting, the CPU fan speed is deliberately kept 1.2~1.7V higher than the SYS fan speed. This is probably to reflect the higher heat generated by the CPU and its greater need for cooling. Here are some spot-checked numbers:

Fan
50%
60%
70%
80%
90%
100%
CPU
6.7V
7.9V
9.1V
10.2V
11.1V
12V
SYS
5.5V
6.2V
7.5V
9.0V
10.5V
12V

The minimum voltages of 6.7V and 5.5V are a bit higher than most silent PC enthusiasts would like, but with a quiet 12V fan, it is low enough to make the fan inaudible inside a PC. I personally would have preferred 4V or 4.5V as a minimum.

RPM is also shown if the fan is equipped with the third RPM sensing lead. In the screen directly above, both fans have RPM sensing and are showing 1450 and 1950 RPM, respectively. In the main setup menu further above, one RPM equipped fan is shows 650 RPM; the other fan does not have a speed sensing output. RPM sensing output in the fan is required for this and some other key functions in the Windows-based SilentTEK to work fully.

3. Fan Mode is an oddity related to Juke Box, mentioned above. It let's you choose the operation of the fan with the system in POST mode. What in the world for? Why worry about fan behavior for the few seconds that the system will be in transition between POST and the OS?

AOpen offers a feature called Juke Box, basically a CD Player, in many of its mainboards. Juke Box does not work in any normal OS. Instead, it works from within POST. The Juke Box is selected manually or automatically during boot so that a CD can be played without waiting for the OS to boot. AOpen decided that just setting the fan speed (50-100%, under Boot Speed) is not good enough in case you use your PC in Juke Box mode for long stretches of time.

Here are the options:

A. Full speed: All fans are driven at 12V while in POST or Juke Box. This setting overrides the previous 50-100% speed setting for the fans.

B. Smart Control: Target temperature for CPU and SYS are defined. The fan speed is then sped up, slowed and stopped automatically to keep the temperature within target. If the cooling system is capable of keeping in the target temperature, Smart Control will maintain it within a 2 degree range.

C. Fixed Speed: The fans can be set to run at any speed in POST or Juke Box from 0% to 100%. A setting of 5% was measuring to be ~3V on either CPU or SYS fan. This is not enough voltage to start many fans. AOPen need to re-think these numbers, probably change the minimum to a safer 4.5V. Again, this appears to ride the previous 50-100% speed setting for the fans.

Remember, the Fan Mode setting only applies for POST or Juke Box mode!

4. The remainder of the Silent BIOS / HW Monitor menu is devoted to displaying information about voltages and fan speeds. The sharp-eyed will note the CPU Kernel Temperature display, something we have not encountered before.



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