Dell Optiplex XE2 SFF Manual Fan Control

Hello Everyone,

I have recently purchased and upgraded a Dell Optiplex XE2 SFF PC. The form factor is awesome and it's safe to say I've absolutely fallen in love with it. I've upgraded the CPU to a Xeon E3-1281 v3 and installed a Geforce GTX 1650 LP among some other upgrades. It's really nice having this much power in such a small form factor, however the heat generated by these parts has become a bit of an issue.

I know that, for whatever reason, Dell has always been quite shy to give the user control over the fans in the system. This is the case for the XE2 as well. There is an option in the BIOS to "Override Fan Control" and have the fans run at max speed all the time, but the amount of noise generated by the fans at this speed makes this option pretty unattractive.

I did some digging and found that HWInfo64 can offer some pretty good fan control, but upon closer inspection, it seems that Dell has really outdone themselves at locking down the fan speeds this time... HWInfo64 reports that the only speeds I am allowed to run the fans at are 0 RPM (which in reality sets the fans at around 500RPM a piece), 1000 RPM, or 5200 RPM. This makes absolutely no sense to me. Considering that Dell spent the extra cash to install PWM fans in the system, the fact that the built in EC can't even use a PWM fan curve has me completely baffled.

However, there is a program written by one Aaron Kelley that attempts to disable the Dell managed fan control and give you manual access to set the fan speed. Supposedly this works a treat on Dell laptops, since the EC isn't locked to three speeds. However, on my Optiplex XE2, this just means I can manually switch between the three EC defined setpoints, not exactly a fix. I did, however, manage to create a crude means of fan control by using this program. I have created a batch script that toggles between the 1000 RPM setpoint and the 5200 RPM setpoint. Exploiting the built in fan hysteresis used by the EC, I can effectively create new "setpoints" by changing the ratio of how long the system spends toggling between the low and high setpoint.

For example, I set the EC to switch between the 1000 RPM setting and 5200 RPM setting every three seconds. Because it takes the fan a considerable amount of time to spin up/spin down to each setpoint, the fan effectively runs at 2300 RPM with minimal change in noise level. This is a horrible way of doing this, and I would imagine it causes quite a bit of extra stress on the fan, but I can't see any other way of doing it unless someone figures out how to access the PWM to control the fan.

There is one program that I believe has come close to getting this figured out, however it's pretty unfinished and buggy and requires enabling test signing via bcdedit which is a MASSIVE security risk. However, by using the "override EC" radio button I am able to use the sliders to access the three fan settings, and by mashing enough of the debug buttons (seriously, like randomly hitting the debug buttons until it works) I am sometimes able to take manual PWM control of one of the fans, however it seems that which fan is selected for the PWM control is random, or at least selected by a method that I don't understand. This means I am able to use the slider to increase or decrease the speed of the fan in an extremely granular fashion, and set it exactly to where it's spinning quite fast, but not fast enough to be audibly annoying. This tells me that PWM control of the system fans is possible, but it hasn't been fully fleshed out yet.

So has anyone had any better luck with this? Anyone been able to get that second program to work any better? Is there any other way to manipulate the EC into giving the user control over the PWM for the fans?

Thanks everyone