PWM vs DC fans: Which should you buy for PC cooling

[Admin]

With DC and PWM fans available, and DC fans sometimes being cheaper, which should you opt for, 3-pin DC or 4-pin PWM?

PWM vs DC fans: Which should you buy for PC cooling : Read more

 

[bit_user]

These days, three-pin DC case fans are far less common than PWM, for reasons that will become clear as we dig deeper into the differences between the two below.

Didn't someone have a patent on using PWM fans in PC cooling? I thought that was why motherboards have traditionally been so stingy with PWM fan headers (i.e. except for the CPU fan). Did that expire, recently? My latest motherboard (admitted, a higher end model) has PWM headers for just about everything!

 

[TheyCallMeContra]

Didn't someone have a patent on using PWM fans in PC cooling? I thought that was why motherboards have traditionally been so stingy with PWM fan headers (i.e. except for the CPU fan). Did that expire, recently? My latest motherboard (admitted, a higher end model) has PWM headers for just about everything!

I'm unfamiliar with this, but having written an earlier version of this piece with some history around the connectors...was it Molex, perhaps? It seems both DC and PWM fan connectors are Molex in origin, so if anyone was charging for PWM it was probably them.

 

[bit_user]

I'm unfamiliar with this, but having written an earlier version of this piece with some history around the connectors...was it Molex, perhaps? It seems both DC and PWM fan connectors are Molex in origin, so if anyone was charging for PWM it was probably them.

Maybe this is what I remembered hearing about?

Baffled by Arctic Cooling Patented PWM Sharing Technology

I now have in hand some ARCTIC F PWM fans, with their patented PWM Sharing Technology. I can described exactly how they are wired, and how they are to be used. I do not understand what aspect of this design could be covered by a patent. These fans are advertised as being able to be...

forums.anandtech.com

It was probably at least 10 years ago.

While doing a little searching for what I remember hearing about, I happened to run across this 2005 Intel specification for 4-wire PWM fans:

https://www.intel.com/content/dam/support/us/en/documents/intel-nuc/intel-4wire-pwm-fans-specs.pdf
​

Its initial publication date is Nov 2003. So, I think that would put us safely outside the window of any patents that might've covered core aspects.

 

[Notton]

It's not mentioned in the article, but you can control PWM fans by adjusting its DC voltage.
Not that I would recommend it because lower DC voltage than specified can cause the motor to click and defeat the purpose of quieter operation. DC fans also suffer from motor clicking to a certain extent and part of the challenge before PWM became popular was finding the fans that didn't have this problem. The clicking issue is usually less of a problem on fans with less inertial mass. 120x32 and 120x38 were very prone to it.

Back in those days, Antec and Scythe/NMB/Panaflow were top picks for DC fans. Noctua pretty much perfected it after they entered the market.
If you can find low usage DC fans made by those companies, they still work extremely well. Or rather, their motor and bearings are amazing at keeping additional noise low.

I still use some really old Scythe/NMB fans from the P4/AM3 era. I've repurposed them for a laptop cooler and they work dead silent at 5V. It cools way better and quieter than the junk laptop cooling pads available for purchase.