Smart Case Fans...

Now that the 70 degree F + weather is here I'm becoming more frustrated with these Smart Fans. The 80mm fans are great. Stick a temperature probe under the CPU heatsink and the 80mm fans ramp up their speed as the temperature at the probe increases exactly as you'd expect. The only problem is that I have a 120mm fan on my CPU heatsink and I can hook it up to the same probe that works great on the 80mm and it does NOTHING! I've finally had to resort to using the fan speed control knobs that come with the fans. I have 2 knobs, one for the 120mm front intake and one for the 120mm CPU fan - all of my fans in Ziggo5 are the Thermaltake Smart Fans with Blue LEDs.

Each Smart Fan comes with an optional speed control knob which is mounted to a PCI slot cover from Thermaltake. Not bad, but I don't have 2 slots at the back of my machine I want to sacrifice to this unholy compromise. The knobs are silver so they won't be going on the front of my machine. So I grabbed a blank Lian-Li slot cover, made my marks and started drilling holes. The slot covers must be made out of steel (as opposed to aluminum like the rest of the chassis) because they put up a good fight when I was drilling into them. Most knobs you might find on a device are mounted through a hole in a surface and then there's a nut that goes onto the knob shaft. Not so with these knobs. The Thermaltake slot covers have a rectangular cut made on either side of where the knob goes and then the metal was bent inward to make a sort of U shaped knob holder. The knob's square body fits perfectly into the U shape and there are 2 tiny latches involved as well. Right... all this means is that I was not going to be able to mount the knobs on a blank slot cover the way I'd hoped, but I made it work. I now have the 2 knobs mounted on a single PCI slot cover with plenty of room to add 5 or 6 knobs in I ever had the desire - which I'm sure I never will.

Once I had the knobs mounted (with some super glue help) I put the slot cover in place and hooked up one control to the 120mm CPU fan and booted into the BIOS to check things out. Just because I can, I left the temperature probe attached to the fan also. The first thing I noticed was that with the knob on it's lowest setting the fan was running 100+ RPM faster than it had without the knob. It used to hover around 1350 RPM and was at 1480 according to the BIOS. Interesting.

Next, of course, I booted into windows and started the dual Prime95 tests to heat things up. I had run this test before I started to get somewhat accurate results - rather than comparing to my old test results that were taken when the ambient temperature was a good 20 degrees F cooler.
Start test: (before the knobs, with temp probes)
CPU = 62, MB = 44
CPUfan = 1371, 80mm = 3590, 120mm = 1360
5 minutes into test:
CPU = 68, MB = 46
CPUfan = 1360, 80mm = 4821, 120mm = 1360
8 minutes into test:
CPU = 70/71, MB = 49
CPUfan = 1350, 80mm = 5113, 120mm = 1339
I stopped the test at this point to start working on the fans. Both 120mm fans were plugged into motherboard headers for power. I decided to change that and plug them into 4pin molex connectors from the PSU using adapters which also allow you to run the 3rd wire to the motherboard header to monitor speed. This adapter comes with the fans.
I had set the knobs so that both 120mm fans were around 1500 RPM.
Start 2nd test: (CPUfan has knob and temp probe at CPU heatsink now)
CPU = 45, MB = 35
CPUfan = 1534, 80mm = 1654, 120mm = 1430
1 minute in:
CPU = 54, MB = 35
CPUfan = 1721!!!!! 80mm = 1776, 120mm = 1406
6 minutes in:
CPU = 54, MB = 37
CPUfan = 1785, 80mm = 2136, 120mm = 1430

This is interesting. I'm now seeing the 120mm CPUfan increase it's RPM with the temperature I think! All I had to do was hook up the knob AND the temp probe. It could be an anomaly... but I don't care. What I do care about is that my 80mm rear intake fan shouldn't be overworking itself anymore. I ended up setting the 120mm fans to appx 1700 RPM. Since one is an intake on the front I think that will help slow down the 80mm intake at the rear (with temp probe at CPU heatsink and no knob) and bring in more air. The front intake 120mm has a temp probe under the heatsink of my ATI x1950xt and I don't expect to see any changes from that position. The leads of the probes aren't long enough to reach the front fan from the CPU heatsink so that's why I have that one there. Some day I might take some temp readings on the hard drive and see if the probe for the front intake would be better off there.