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

Dec 29, 2002 -- by Mike Chin

Product AOpen SilentBIOS / SilentTEK in AX4GE Max P4-478 motherboard
Manufacturer AOpen
MSP "Free" - Feature is embedded in a large number of AOpen motherboards released since November 2002

It is becoming increasingly difficult to find meaningful differences in PC hardware products. Take motherboards, for example, which are grist for the daily mill of PC hardware review web sites. Given the latest and greatest chipset release from Intel or VIA or SiS or..., the various competitors quickly trot up an enormous array of motherboards that appear to deviate from the reference product only by its heatsink and the color of its printed circuit board! The buyers are expected to choose, then, on the basis of packaging, brand, and features.

A comparison review of 13 new 845GE motherboards by Tom's Hardware Guide earlier this month showed once again that performance differences between first and last in a group of same-chipset motherboards is tiny -- no more than 4%, in this case, but for one underachiever. You can measure the differences but it is almost impossible to perceive in actual use.

Perhaps this sameness beneath the skin is a testament to rapid development cycles in the industry. Manufacturers no longer feel they have the luxury or time to fine-tune the latest components because their competitors would use that time to clean up in the marketplace. No one can afford to wait. So rather than offer superior execution, parity in performance is offered -- along with more bells and whistles in features to persuade the buyer.

So which features? The answer seems to be expanding, as usual. In the battle for features, the inclusions on motherboards are staggering, even compared to just a scant year or two ago. A quick visit to any major motherboard maker's product pages will have you reeling...

Support for 533Mhz FSB, DDR400 memory, ATA133 IDE, Serial ATA on-board, Hyper-Threading Technology, High-end Audio Grade Capacitors, CPU Jumper-less Design, 1MHz Stepping CPU Overclocking, Adjustable CPU Vcore, AGP and Memory Voltage, Low ESR Capacitors, Watch Dog Timer, AGP Protection Technology, CPU Over Current Protection (OCP), Hardware Monitoring, IDE RAID,100/1000 Mbps PCI LAN Chip, 5,1 Channel Sound built in, etc, etc...

And that is just a very small sampling, of course.

When it comes to the killer motherboard feature of the season, however, it is none of the above. For those who try to achieve the quiet PC operation that most of the industry still seems to consider irrelevant or unprofitable, the killer motherboard feature of the season was just launched in November by AOpen on 140(!!) of its motherboards: SilentBIOS and SilentTEK. There was barely a murmur of acknowledgment by the technology press other than SPCR's own coverage of their press release.

AOpen's Killer Motherboard Feature

SilentBIOS/TEK is a sophisticated thermal-noise fan management system. The system allows the user to establish a feedback loop between CPU temperature, as reported by the CPU core thermal diode, and the voltage that controls the speed of the cooling fan(s). The incorporation of CPU thermal diode reporting of temperature gives the system a high degree of consistency and accuracy.

This feedback control loop can be defined with precision. SilentBIOS is embedded in the motherboard, accessed via the BIOS, and its control extended into all recent flavors of Windows through a software utility called SilentTEK. According to AOpen,

The fan control function is based on the motherboard's Super I/O signal. The Super I/O (in the AOpen AX4GE Max motherboard, this is Winbond W83627HF) reports the CPU temperature and fan speed. The fan speed is controlled by using an onboard IC. So the Silent Tek/Bios is almost completely software-based, which makes the processing more flexible.

AOpen has catapulted PC thermal / noise management to a level that has hardly been imagined by even silent PC diehards in SPCR's own forums. With one of these new AOpen motherboards, gone is the need for any external fan controllers, fan bays, system monitors or general purpose thermal speed fans. Whether conventional air-cooling or water cooling is utilized, maintaining the balance between cooling and noise can be neatly carried out by SilentBIOS/TEK. Their implementation of embedded thermal / noise control is so far in advance of the competition that AOpen looks like a warrior wielding a sword of steel against contestants armed only with sticks.

This is not to say that SilentBIOS/TEK is without deficiencies. It is the first iteration of a software utility; it almost goes without saying that flaws and inconsistencies are part of the current package. One can expect these problems to be improved in future patches or releases. For the time being, however, AOpen has no serious competition in an embedded motherboard thermal-noise solution.

The AOpen AX4GE Max

AX4GE Max: One of at least 140 AOpen motherboards now equipped with SilentBIOS/TEK

SilentBIOS/TEK was examined as implemented on a new AX4GE Max motherboard sample for P4-478 submitted by AOpen. One of the models that fared well in the aforementioned Tom's Hardware review, AX4GE Max is an extremely well-equipped new motherboard based on the recent Intel 845GE chipset. The board's long roster of features is fully detailed on AOpen's web pages. In terms of suitability for testing, the unit's independent settings for FSB, AGP/ PCI and CPU speeds, plus CPU Vcore from 1.1 to 1.925 volts are very useful.

The BIOS-implemented SilentBIOS basically provides a simple speed control for two fans that applies regardless of the OS in the system. SilentBIOS may be the prerequisite for the Windows-based SilentTEK, which adds a plethora of noise / thermal control functionality. Fan control passes from SilentBIOS to SilentTEK when the latter is turned on.

The test PC assembled for this review is described in full below:

Intel P4-1.8A CPU Rated at ~50W max. at stock. Overclocked to 133 MHz FSB for 2.4 GHz CPU speed with Vcore raised 0.1V to 1.6V.
AOpen AX4GE Max motherboard Built-in VGA and LAN used.

BIOS version R1.05c Beta, 2002/12/02
SilentTEK Version 3.1.00
Thermalright AX478 HS Very good P4 heatsink
256 MB DDR RAM Samsung 2100
Seagate Barracuda IV 40G Single-platter, 12.8W max
Hitachi 16X DVD ROM Detailed specs unknown
Antec Sonata case + True 380S PSU Recently reviewed case and PSU
Fans

Large variety of mostly 3-lead 80-120mm fans

OS Windows XP Pro, SP1

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.

INTO WINDOWS: SILENT TEK

SilentTEK is compatible with Windows 98SE, ME, NT, 2000 and XP. Linux is not an option at this time. The test system was loaded with Windows XP Pro, SP1.

The CD that accompanied the motherboard did not contain any software called SilentTEK. The closest match was Hardware Monitor III. Installing this software appeared to load SilentTEK, with the exception of the CD drive speed control. AOpen clarified that Hardware Monitor III and SilentTEK are one and the same. HW-III displays itself as SilentTEK when the fan control function is activated as per Enable FAN Speed Control on this menu:

Main SilentTEK Control Screen

This brings us to the heart of the software. There are 4 fan control modes. Here is AOpen's explanation of these modes:

I. Smart FAN Control: This is the default setting of SilentTek and can be used for any branded computer housing. With a special innovative algorithm developed by AOpen, the fan speed is automatically adjusted by the factors of CPU and ambient temperature. If you are not running too many applications with heavy loading, you may find your CPU fan is almost always running at zero RPM. Ease-of-use and trouble free at your service.

II. Fix FAN Control: In this setting, you may set a fixed rotation speed for each fan you installed.

III. Multiple Control: This is the most unconstrained setting, which allows you to be on top of all details and set different rotation speed for different temperature.

IV. AOpen Recommend Setting: This is the best setting to fit in with AOpen housing, SilentPC would keep your system under the least quiet situation, and would only lift the fan rotation speed for heat-dissipation when necessary. According to our practical testing, we found that in most cases, the fan would remain still when the CPU is not in full loading.

Furthermore,

CDROM Noise Control: Some AOpen CDROM/CDRW/DVD drives have implemented speed control function, when combined with SilentTek, you can control drive speed to reduce noise. (This feature was also available with the DVD-ROM drive used in the test system.)

Let's examine each fan mode in more detail.

I. Smart Fan

Selecting Smart Fan Control brings up this dialog box. The numbers shown indicate the maximum target temperatures in Celsius. CPU refers (on this board) to the diode temperature reported by the P4, and System refers to the temperature of the onboard thermometer.

The fans are left NOT running until the temperature reaches the target maximum. The fan is then turned on only long enough to drop the temperature a couple of degrees below the target, then stopped again.

During stress testing of the CPU, the voltage fed to the fan in Smart Fan mode varied considerably, from the full 12V down to ~6V and many points in between. During stress testing, Smart Fan mode kept CPU temp within +,-2C of the target maximum temperature.

II. Fix Fan

Fix Fan is the equivalent of a manual fan speed controller. It lets you select the fan speed as a percentage, from 0% to 100%. Selecting 0% stops the fan altogether. The fan speed is shown only if the fan is equipped with the third speed monitoring output wire.

The output voltage for the two fan headers is not linear or the same. The table below shows the outputs at each setting. Obviously, this refers specifically to the AX4GE Max board reviewed, and may be different with other AOpen motherboard models.

%
5-10
15-35
40
45-55
60
65
70
75
80
85
90
95
100
CPU
6.4V
7.25V
10.25V
7.25V
7.75V
8.34V
8.93V
9.5V
10.1V
10.6V
11.2V
11.6V
12V
System
5.25V
5.83V
9.16V
5.83V
6.22V
6.8V
7.46V
8.14V
8.96V
9.78V
10.68V
11.33V
12V

The obvious anomaly is the bump at 40%, the 9th position on the slider scale. This 10.25V/9.16V bump looks like a programming error. The voltage across the range varied ~5%, which is probably within the cumulative accuracy tolerance of the measurement and voltage delivery systems. As you can see, despite the 20 discrete steps, there are only 12 different voltage settings.

III. Multiple Level

Multiple Level Control is by far the most sophisticated mode. It is probably too elaborate for the vast majority of users. Let's look at just the CPU Fan settings. (The sharp-eyed might see the amusing misspelling tempuratrue and tempurature. Perhaps the programmers were doing too many Japanese lunches.)

There are 6 trigger points that can be defined, ranging from 0C to 100C in 0.5C increments. A fan speed and temperature can be set for each of the six trigger points. There are only two limitations on the fan speed and trigger point options:

1) The temperature set for any of the 6 points must be at least 0.5C higher than the previous point and 0.5C lower than the next point.

2) The fan speed set for any of the 6 points can be no higher than the next point.

You are free to...

3) Define any number of trigger points, from 1 to 6.

4) Define the first trigger point at any temperature up to 97.5C.

There are 20 points on each fan voltage slider scale. Not surprisingly, this scale is the same as the one found in the Fix Fan Control mode described in the previous section and has the same voltage bump at the 9th point.

A great deal of flexibility is possible. Here are some simple examples:

A. Quiet but safe: An exponential relationship between CPU temperature and fan speed for low noise cooling under most conditions, yet full power cooling at high stress.

Trigger
1
2
3
4
5
6
Temp
54C
55C
60C
61C
62C
63C
CPU
0V
7.75V
8.34V
9.5V
11.2V
12V

This setup keeps the fan from turning on at all until the CPU reached 55C. With a middle-power CPU and a topnotch, low-airflow heatsink, this condition might prevail most of the time. At 55C, the fan turns on at the lowest possible speed. With a Panaflo or similar, this transition may not even be audible. This minimal fan speed may be enough most of the time to keep the CPU temperature from reaching 60C, which is perfectly safe with most CPUs. If the temp keeps rising above 60C, the fan accelerates to full speed very quickly to ensure that the full cooling power under high stress conditions.

B. Higher temp version of A: Simply shifts all temps up by 5C for those who are comfortable with a higher level of risk. Alternatively, this would provide the same level of noise performance in an ambient temperature that is 5C higher.

Trigger
1
2
3
4
5
6
Temp
59C
60C
65C
66C
67C
68C
CPU
0V
7.75V
8.34V
9.5V
11.2V
12V

C. Linear: This setup would keep the fan at a slow speed in most conditions and change its speed up and down more steadily. It will tend to provide lower average temperatures and a higher level of noise. Likely does not require as high heatsink performance as the previous examples; the main drawback may be the audibility of changes in fan speed. (But the changes are relatively gradual.)

Trigger
1
2
3
4
5
6
Temp
34C
35C
40C
45C
50C
55C
CPU
0V
6.4V
7.25V
8.93V
10.8V
12V

D. Off/On: Here is an extreme low-noise setup. Fan stays completely off until CPU hits 65C, then comes on full speed. The temps set for points 1-4 have no effect whatsoever.

Trigger
1
2
3
4
5
6
Temp
20C
35C
40C
45C
64C
65C
CPU
0V
0V
0V
0V
0V
12V

Each user should experiment to establish a Multiple Control algorithm that works well for his/her system.

IV. AOpen Recommend Setting

There is no dialog box or submenu for this option, as it is completely preset. AOpen says the Recommended Setting is based on profiles of the specific CPU type (P4 1.6, 1.8, 2.0, 2.2, 2.4 GHz), and collated temperature, fan and noise data. These profiles are converted into optimal values in Multiple Control mode. It's somewhat generic, but may be worth a try.

OTHER SILENT TEK FEATURES

There are 7 other tabs on the HW III / SilentTek interface. For the sake of brevity, screen shots with minimum text are provided here, as they are generally self-explanatory.

The Graphic functions can be very useful for analysis. Here are some examples:

SILENT BIOS/TEK IN ACTUAL USE

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.

Trigger
1
2
3
4
5
6
Temp
59C
60C
65C
66C
67C
68C
CPU
0V
7.75V
8.34V
9.5V
11.2V
12V

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.

CONCLUSIONS

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

http://www.silentpcreview.com

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