Author Topic: Q: What RPM should a CPU fan spin at? (Read 601 times)

Swoop · « **on:** May 29, 2005, 08:24:25 AM »

Just wondering.

Roscoroo · « **Reply #1 on:** May 29, 2005, 10:47:31 AM »

3800-5500 id guess depending on the fan and heatsink .

mine's spining at 4383

Ecliptik · « **Reply #2 on:** May 29, 2005, 03:53:40 PM »

Totally depends on the size of the fan. The bigger the fan, the more air it can move per revolution and the slower it needs to spin. I use a Panaflo 92mm case fan on my CPU that spins at about 3000 RPM, for a CPU fan 92mm is large. My previous fan was a 70mm that could spin at 6000 RPM. Large fans have the advantage of spinning slower and thus being much quieter than faster spinning small fans. But, small fans have smaller "dead zones", which is the area directly beneath the fan engine housing that gets the least airflow, and can thus sometimes offer superior cooling, but to accomplish this they need to spin at very high RPM and will be very noisy. The largest fans people can usually mount on a CPU are 120mm, which can spin at less than 2000 RPM (super quiet), but you need an appropriately large heatsink to take advantage of all that area.

eagl · « **Reply #3 on:** May 30, 2005, 03:46:54 PM »

In my experience, most 80mm and 92mm fans start to make noticeable noise above 2500ish rpm. YMMV and some fans are much quieter than others, so if you have a couple, try them out.

My rule of thumb is to start with the fan slow (1600ish rpm) and slowly crank up the fan until I can distinctly hear it, then lower it by about 100 rpm. Then load up the cpu and see if the fan keeps it cool enough. The only problem I've ever had with this method is that I tuned too many fans to the same rpm and my entire case started resonating

I had to increase the speed of one of my intake 80mm fans and drop the speed of the other one waaay down to stop the resonation. It sounded absolutely horrible, making about as much noise as my car from 10 ft away.

llama · « **Reply #4 on:** May 31, 2005, 06:45:32 PM »

There's a great freeware program called SpeedFan you may want to check out. (http://www.almico.com/speedfan.php)

If your hardware is compatible, and has temperature sensors, Speedfan can lower the speeds of your CPU, case, and (sometimes) video card fan when temperatures are low and you're just typing in Word or surfing. When you play games and such, the temps go up, and Speedfan raises the fan speeds to whatever you want (such as 85% of max). If temps go into a "critical" zone (defined by you also), the fans will spin at 100%.

It is very powerful and flexible, and can definately quiet your computer when you aren't playing games.

You should consider checking it out.

-Llama

68DevilM · « **Reply #5 on:** June 05, 2005, 10:54:19 AM »

my cpu fan spins at 2192 with minimal load

chassis fan is at 2679.

now i have 2 other fans that i have no idea what thier doing.

no tweaking here all is at factory settings.

how do you decrease anyways?

lower voltage in bios?

llama · « **Reply #6 on:** June 08, 2005, 01:18:14 PM »

Are you not reading these posts?

USE SPEEDFAN to measure these things.

-Llama

Ecliptik · « **Reply #7 on:** June 10, 2005, 02:07:30 PM »

I use Speedfan, it's a handy tool for monitoring temperature and fan RPM but it's just reading the same motherboard registers that the BIOS is to get the information. You will only be able to adjust fan speed (voltage) if your motherboard supports that ability, or if you put regulators on the fan power headers to adjust manually.

There are 10 fans in my system. You can only use software to monitor as many fans as there are fan sensor headers on the motherboard. So most of the case fans I can't read.

eagl · « **Reply #8 on:** June 10, 2005, 03:14:14 PM »

You can find fan speed adjusters at stores like newegg. I think newegg had a nice one for about $8. It just plugs in between the fan and the power source, and then you adjust a knob on the speed adjuster to vary the fan voltage.

Or you can do what I did, and buy either a fan with a built-in thermocouple that automatically adjusts the speed to the temp sensed by the little probe, or a fan with a built in manual speed adjustment.

I have both. The temp sensor fan is my rear exhaust fan, and the probe is wedged into my vid card heatsink. When my vid card gets hot, that fan speeds up to help exhaust the air heated up by the vid card. The manual one is a front intake fan, and I adjusted it to kill that fan resonance problem I had. My cpu heatsink fan is also adjustable, and I tweaked it so I can barely hear it and that's plenty of airflow when coupled to my kickprettythang thermalright XP-90C heatsink.

The last adjustable fan I have is inside my power supply, and again I have it turned down so I just barely can't hear it over the other fans and hard drive. That seems to also be plenty of airflow. If it ever gets really hot in my office and I still need to use my computer, all I have to do is turn up the cpu fan and the PSU fan, and I can drop case temps by up to 10 deg F and cpu temps by about 5 deg F.

eagl