Setting a Minimum CPU Fan Speed (CPU Fan Speed Not Constant at Idle)

[purefusion]

I have an AMD FX 8350 CPU (currently with stock cooler/HSF) on a Gigabyte GA-78LMT-USB3 mobo (rev 5.0).

When my CPU is idle, the CPU fan speed constantly varies between 2170 RPM and 2336 RPM (and several speeds in between). This lack of a single constant RPM speed results in a change in audible frequencies that generates a subtle but annoying hum/whir sound at some of these lower frequencies. Seems like anything above 2500 RPM doesn't have that annoying hum that comes and goes with the frequent changes in CPU fan speed.

Is there a way to set a minimum fan speed RPM on the CPU fan? I was toying around with SpeedFan but couldn't figure out how to set any kind of minimum RPM (though I'd rather not have to rely on a software solution, if it can be avoided). If there's no better way to handle something like this, I guess I suppose I'd keep it installed. However, I don't want to disable the CPU Smart FAN Control in the BIOS and make the CPU fan run at max all the time.

Here's a screenshot of that part of the BIOS: http://i.imgur.com/l0ZSOy7.jpg

 

[laviniuc]

install the easytune app and adjust the fan control limits, i had a similar issue when i upgraded my cooler.

 

[Branden Bowser]

like @Iavniuc said, easytune is how to do this. I have the same MOB however, and even with the easytune I was not able to change the speed of the fan. You have to make sure that the fan itself supports a range of RPM's that can be set. And the fact that it changes while idle means that you either have poor air flow, or that you got some thermal paste in the fan itself or it is clogged some how. check the fan, make sure that It is clean. And make sure that you have the CPU fan plugged into the correct fan slot on your MOB.

Also, what is your powersupply? a poor PSU can affect the speed(s) of the fan(s) by providing too much voltage to the MOB and thus your fan will appear to spin faster when there is a power surge comming from your PSU. If it is an ULTRA LSP series I would change it asap. I had this PSU before, and it caused my RAM to recieve 1.5 - 1.9V which would crash my PC , as well as make the fans speed change randomly.

 

[purefusion]

I guess I was a little loose with the term 'idle' ...the fan speed changes are correlating to a very slight increase in CPU usage or temperature. But still, these lower RPM frequencies are annoying. Would prefer to set it to a minimum of 2500 RPM if possible. There's no hum at 2500 or higher, so I'm guessing the resonance frequency of the 8350's stock HSF is somewhere in the 2300's.

Power supply is a 750 Watt Corsair. Don't know the exact details though.

 

[Branden Bowser]

I guess I was a little loose with the term 'idle' ...the fan speed changes are correlating to a very slight increase in CPU usage or temperature. But still, these lower RPM frequencies are annoying. Would prefer to set it to a minimum of 2500 RPM if possible. There's no hum at 2500 or higher, so I'm guessing the resonance frequency of the 8350's stock HSF is somewhere in the 2300's.

Power supply is a 750 Watt Corsair. Don't know the exact details though.

Okay that is a good PSU. And i've had that issue with most of the HSF for any AMD CPU. I would suggest getting a different one, coolermaster makes a great fan. It is what I use and it is really quiet. And I have 3 fans, one on the top, one on the back, and the CPU fan. Plus it keeps the computer cool enough so that the CPU fan never increases in RPM and the temps inside the computer all around stay at a balmy 27 C. The stock HSF's do not come with a manual RPM adjust. They will trottle in order to cool the CPU but will not allow you to manually set the speeds. I have a GA-78LMT Motherboard and i had this issue from the start until I got a new fan. its the best way to fix it in my opinion.

However if you cant afford a new fan, then I would get CoreTemp. Look at the temperatures and post them here. Do an Idle, and a load (Like leave a game running for about 15 mins) and then look at the temps. If they stay pretty close (like 30 idle - 34/40 load) then Your fan is doing its job and will just be loud.

Like I said if the issue is just the noise then I would swap it out for a new fan. They are like $15 for the more expensive ones. But you will love it trust me.

 

[purefusion]

Like I said if the issue is just the noise then I would swap it out for a new fan. They are like $15 for the more expensive ones. But you will love it trust me.

Thanks Brandon. It's not so much the noise of the fan in general that bothers me. Even at 3000 RPM, it's still not that loud to me (it doesn't have an annoying resonant hum at that speed). Just the 2200 - 2400 RPM range has the hum (and only at certain RPM levels, not every level in that range is annoying, but the constant change of RPM cycles through RPM levels that do have the hum. I almost wish I could tell it to keep the CPU fan speed constant until the temp changes by more than a few degrees.

For what it's worth, I did install the Easy Tuner. I was able to manipulate the lower and upper fan speed thresholds by going to the "Smart" tab, chosing "Advanced" and adjusting the two nodes shown on the list (which adjusts the % RPM at a low temp and the % RPM at a high temp). The default is showing as 28%/20C and 100%/66C. I bumped the first node to 48%/40 and the fan is now idles around 2419 RPM which is slightly higher but less annoying than the 23XX RPM levels that were giving the resonant hum.

I do actually have a Zalman 9900 Max but I wanted to see if the stock HSF would suffice because I wasn't planning on overclocking, even though I have the FX 8350 (Black Edition) and a good mobo for overclocking. Mostly just didn't think I had time to investigate all that there is to overclocking, and this upgrade is already so much better than my prior computer even with the stock 8530 HSF. It's as if I've purchased a new Tesla P85D and decided to keep the acceleration mode set to "sport" rather than "insane". Of course, overclocking is probably a bit more complicated than flipping a switch in the control panel.

That being said, I'm curious about potentially overclocking my memory. I have DDR3 1866 in there now, but the mobo only claims to support up to 1333. I had another board (ASUS M5A78L-M/USB3) that supported it, but read a lot of negatives with the other board, especially that it didn't have enough power to give my 8350 full potential. Not sure if I'd see a significant difference between 1333 and 1866, or if I even can overclock it up to 1866 with this board, but I have no idea what I'm doing to that end, so perhaps that's better left to another thread.

 

[Branden Bowser]

I would shy away from OC'ing your memory unless it is Ram geared towards over clocking. What manufacturer of ram is it?