Allow us to show you how to use Speedfan to program your case fans to spin slow ‘n’ quiet at idle, and to automatically throttle to full-speed when you need more cooling power.

Speedfan is a wonderful utility that’s absolutely free! It lets you keep track of your motherboard and CPU temperatures, your fan speeds, and the voltages from your power supply. You can even use it to automatically control your fan speeds. With a little tweaking, you can program Speedfan to spin your fans up and down according to temperature thresholds that you determine.

The upshot is this: You can keep your PC nice and quiet during low-impact tasks such as trolling the Maximum PC forums, but crank up the fans to keep your hardware cool when you’re playing a game or rendering video.

We’re going to show you how to configure Speedfan so that your CPU fan’s speed automatically adjusts in response to core temperature changes. Speedfan is definitely a power user’s app—it will do whatever you tell it to, even if that might potentially damage your hardware. Be careful!

While Speedfan supports dozens of motherboards, there are many models that don’t allow fan-speed changes. Some motherboards might not even display temperatures or fan speeds. Check the Speedfan homepage for a list of supported boards; if your board isn’t listed you’re probably out of luck.

1. Examining the Main Screen
The first time you fire up Speedfan, it takes readings from all of the sensors on the motherboard and gives each fan and temperature reading a cryptic label. In the left-hand pane, you’ll see the reported fan speeds for all of the fans Speedfan detects. Our Asus A8N32 motherboard sports five three-pin fan headers, but we’re only able to read fan-speed measurements for three of them.

In the right-side pane, you’ll see temperature readings from the sensors on your motherboard, as well as the sensor embedded in most CPUs. On our test system, Speedfan reported three temperatures: Temp1, Temp2, and Temp3. We figure that Temp1 is our CPU, Temp2 is the chipset, and we have no idea what Temp3 is, or why it’s running at -128 C. (We’ve seen this before in Speedfan—temperatures that are unbelievably low or high. According to the utility’s author, these erroneous temps are caused by a sensor that is present but not connected. In general, it’s wise to just ignore any reading that seems implausible.) Finally, we see HD0, which is the only hard drive in our rig. In the next step we’ll do some testing to verify which sensor is which.

Below the fan-speed readings are boxes labeled Speed01, Speed02, and Speed03. These usually correspond with the fan speeds listed right above them. You’ll also see voltage readings for the CPU core (Vcore), and for the various rails on your power supply. The power info can be very helpful if you need to troubleshoot a faulty PSU.

Now that you’re familiar with the main window, we’ll conduct some tests to determine which sensors and readouts correspond to particular fans and areas of the motherboard.

 

2. Identify the Sensors and Temperatures
The first thing we want to do is identify which fan readings in Speedfan correspond with the fans in our case. The easiest way to do this is to unplug one of the fans, and then see which reading drops to zero. It takes a second or three for the new speed to register, but on our test motherboard, Fan1 is the fan attached to the CPU, Fan2 is for our rear exhaust fan, and Fan3 is a connector meant to control the PSU fan. Make a note of which fan corresponds with which reading in Speedfan.

Next, we’ll identify the temperature sensors. To find out which temperature is for the CPU, use CPU Burn-in to place a 100 percent load on the CPU (be sure to run two instances if you have a dual-core CPU). After CPU Burn-in runs for a minute or two, you’ll see one temperature jump a few degrees. That number should be the CPU temp. To find out which temp is for the chipset, we recommend temporarily stopping the chipset fan to see which temperature begins to rise.

HD0 is obviously our hard drive’s temperature, since there’s only one reading for a hard drive. If you’ve got more than one drive, you’ll need to shut down your computer, and disconnect all the drives, except your boot drive. Then restart the computer and note the drive reading that shows up in Speedfan. Most RAID controllers block the information that Speedfan needs to report hard drive temperature. If your drives are in a RAID array, Speedfan probably won’t detect any drive temps.

3. Rename the Temperature Readings
Once you’ve figured out which sensor is monitoring which hardware, you need to change the labels within Speedfan.

Click Configure. You’ll be in the tab labeled Temperatures. Here you’ll see the four temperature sensors listed. Click the first item and press F2 to change its name. You should give each sensor as descriptive a name as possible; we named ours “CPU” and “Chipset.” If any of the sensors in your machine report erroneous results (like our third sensor, which reads -128 C), disabled them by unchecking their boxes.

 

4. Rename the Fan Labels
With our temperature sensors renamed, we can now focus on the fan speed labels. Click the tab labeled Fans, and you’ll see the labels that apply to your board. We’re going to rename Fan1 “CPU Fan.” Fan2 will become “Exhaust Fan”, and Fan3 will be “PSU Fan”. If there’s a sensor listed here that is orphaned, feel free to uncheck it so it won’t clutter up the main interface.

Now that you’ve renamed the fans, you have to give the same names to their associated fan-speed readings. Click the tab labeled Speeds, and you’ll see the same three fan speed labels we saw in the Fans tab. Rename each of these with the same names you used previously and click OK to return to the main window.

5. Determine How Much Noise You Can Tolerate
Before you begin automating your fan speeds in the next step, you’ll first have to figure out how fast and slow you want your fans to spin. To do that, you need to crank each of your fans up and down manually, via the main screen.

On the main Speedfan screen, you’ll see three percentage boxes next to the fan names. Each fan is set to 100 percent by default, so you’ll want to slow the fans down one at a time until the temperature is stable and you’re happy with the noise level. To slow the fan speed, click the down arrow. Most fans will stop spinning entirely if you set them below 40 percent. Once you’ve calibrated the first fan, adjust each additional fan in your rig. Make sure you keep an eye on your temperatures, though. Be prepared to crank your fan speeds back up if your hardware starts to overheat!

Not all fans and ports will allow speed adjustments. Only fans that plug into your motherboard report their speeds, and only some ports will allow modulation. On our test board we can monitor fan speed on three out of five ports, but we found we could only control the fan speed on two of those three. If you can only adjust the speeds on a couple of ports, we recommend that you use them to connect the CPU fan and the exhaust fan. Those two fans are the most important when it comes to maintaining good airflow inside your case, and are typically among the noisiest in the system.

 

6. Set Threshold Temperatures
Now for the good stuff: We’re going to set up Speedfan to automatically adjust fan speeds according to temperature thresholds that we determine. Click Configure, and select the CPU temperature sensor. You’ll see two boxes down below labeled “Desired” and “Warning.”

The Desired box is the temperature you would like your CPU to be on a day-to-day basis, even during gaming and other heavy workloads. Use CPU Burn-in to determine what your CPU’s temperature is under full load, then set the Desired temperature a few degrees higher than the maximum temperature you saw under load. For our rig, we chose 40 C for Desired, which is on the low side of the spectrum, but we like to keep our proc chilly. Speedfan will automatically increase and decrease fan speed to maintain the Desired temperature at all times.

In the box labeled Warning, input a value that is very high and would be considered a mini-emergency. When the sensor reaches this temperature, it will bypass all of the settings you have established and crank the fan speed up to 100 percent. Once the sensor’s temperature moves back to the safe zone (a few degrees below the Warning temp), it will lower the fan speed. A common Warning temp would be 70 C. You can also select Desired and Warning temperatures for the other sensors on your motherboard at this time.

7. Set Your Fans' Speed Limits
Click Configure, then click the tab labeled Speeds. Select the CPU fan. You’ll notice there are two boxes at the bottom for minimum and maximum values. The minimum value is the lowest speed that Speedfan will use for the fan. It will spin at this speed as long as the temperature for that sensor is below your Desired temperature.

The maximum value is the fastest speed you’d ever want the fan to spin under normal conditions. We recommend setting the maximum value to the lowest setting your fan can run and still keep your rig at a steady temperature under full load. The fan will spin up to this maximum value when CPU temperature begins to rise. If the CPU temp hits the Warning threshold you set in the previous step, it will crank the fans to 100 percent, regardless of your setting here. Before you click OK, make sure you check Automatically Variated for every fan that you want Speedfan to control automatically. Finally, go back to the main screen and check the box labeled Automatic Fan Speed.