[Stormwind]

HOw can you tell if a fan is any good apart from the rpm? what is CFM anyways and how can you change the voltage so you can force the fan to turn faster?

[sfa ok]

CFM stands for cubic feet per minute, this is how much air the fan acutally moves. You should also look at dba, which is the noise level. Personally, I wouldn't reccommend changing the voltage to bring your fan's rpm up, it's too much of a risk.

[CSaddict]

The best bet is to get the highest CFM fan with the lowest RPM. Its a contradiction in terms I know but that will give you the most efficient fan. If you compare them you'll see. And most of the time the lower RPM fans create less noise.

you use a rheostat or baybus to change the voltage levels of fans although this is done to make them run quieter.

[cjtune]

CSaddict (Jul 29, 2001 11:31 a.m.):
The best bet is to get the highest CFM fan with the lowest RPM. Its a contradiction in terms I know but that will give you the most efficient fan. If you compare them you'll see. And most of the time the lower RPM fans create less noise.

Yup, that's the general practice for sizing (choosing) fans. Lower rpm fans are quieter and cost less dough than 7200rpm Deltas. But if you need more pressure, you have to go with centrifugal fans (you can make you own!) or the super-high rpm axial fans. Power requirements are not indicative of performance between fans of different sizes. My 120mm 80cfm fan eats up only 4.8W but 60mm Deltas require 7W to push 40+ cfm. If you are not gonna change the fan speeds everytime, you can slow down (and thus quiet it down) by just using the 7V line from the PSU or by using resistors to get any voltage in between 7 to 12V or lower.

[Stormwind]

BUt wouldn't a fan with high rpm and more importantly CFM be a better cooler although noise might be a problem. I'm trying to look for fans which are suited from overclocking!

IN my local computer stores, I can only find a brand called "COOL MASTER." Is this good?

I also have another question. What are the measurements for P3, celeron, P4. Athlon and Duron? In other boards they have all there different measurements like 80mm, 60mm etc. BUt aren't the fans used to cool CPU's? Then how come there's all there different measurements?

[cjtune]

The standard fan size for CPU HSFs is 60mm but thickness may vary. Hmm, Cool Master? Seen their heatsinks before but I heard nothing about them in terms of online reviews. Just get any cheap fan you can get you hands on. It's gonna be either noisy or noisier , but performance is the same for the same build but branded ones should be more reliable (won't break down so soon). So far, I have only had one of my fans fail on me and it wasn't a sudden death but rather it was spinning way too slowly -it was a 4-yr old generic-brand Pentium HS fan.

[Stormwind]

So is rpm important. BTW what is ball bearing?

[Shadow ÒÓ]

Stormwind (Jul 31, 2001 09:24 a.m.):
So is rpm important. BTW what is ball bearing?

helps the fan move more smoothly and last longer. Otherwise it uses bushings that rely on low resistance to prevent it from wearing out.

[CalCoolage]

Stormwind (Jul 31, 2001 09:24 a.m.):
So is rpm important. BTW what is ball bearing?

One of the sexes has different ...um... things. So one is ...

Oops. Wrong forum. Things which turn are supported somhow. That is a bearing. If they use little steel balls, that is a ball bearing. Fans can also have sleeve bearings. If you drilled a hole into something and put a shaft into it, the part surrounding the shaft would be a sleeve bearing.

[Stormwind]

WHat is the minimum CFM needed for overclocking?

[cjtune]

Stormwind (Aug 01, 2001 09:47 a.m.):
WHat is the minimum CFM needed for overclocking?

Why don't you check out the reviews of various heatsinks at the main page. You'll find that some of them are designed so well that comfortably low CPU temps can be achieved even with low cfm fans. HS design is basically the upper limit for fan airflow. Some heatsinks won't show any improvement in temps even with really powerful fans, like my slot1 P3 heatsink, which cools the CPU to the same temp regardless of whether I used the stock Intel fan (Nidec corp.) or two generic 60mm fans.