System Cooling
G4 OEM Fan Specifications

G4 Case Fan (Sawtooth, Digital Audio, Quicksilver)

Delta Sensflow WFC1212B 120 x 120 x 25 mm 
12 Volt, 4.32 Watt, 0.44 Amp 
86.52 CFM, 2470 RPM (max), 37.6 dBA 
Thermally regulated PWM

Minebea NMB 4710NL-04W-B37 120 x 120 x 25 mm
12 Volt, 0.32 Amp
88.26 CFM, 2250 (?) RPM (max), 35 dBA
Thermally regulated PWM

Sawtooth PSU Fan

Delta DBS0812H 80 x 80 x 25 mm
4~13.8 Volt, 1.64 Watt, Amp
31.57 CFM, 2850 RPM (max), 30.5 dBA

Gigabit Ethernet and Digital Audio PSU Fan

80 x 80 x 25 mm
4~13.8 Volt, ? Watt, ? Amp
CFM, RPM (max), dBA

Quicksilver CPU Fan

Sunon KDE1206PTV1 60 x 60 x 25 mm
12 Volt, 1.7 Watt, 0.14 Amp
23.5 CFM, 4500 RPM (max), 33.5 dBA
Thermally regulated PWM

Quicksilver PSU Fan

Protechnic 80 x 80 x 25mm 
12 Volt, 0.24 Amp
38.27 CFM, 3000 RPM (max), 29 dBA

MDD Case Fan

Papst 4212H 120 x 120 x 38 mm
12 Volt, ? Amp
108 CFM, 3400 RPM (max), 49 dBA
Thermally regulated PWM

MDD Optical Drive Fan

Delta AFB0612HHB 60 x 60 x 15 mm
12 Volt, 0.18 Amp
17.3 CFM, 4500 RPM, 35 dBA


Minebea 2410ML-04W-B60 60 x 60 x 25 mm
12 Volt, ? Amp
25 CFM, 5300 RPM (max), 38 dBA

Delta AFB0612EH 60 x 60 x 25 mm
12 Volt, ? Amp
38 CFM, 6800 RPM (max), 47 dBA
Replacement Fans

Quiet fans usually come at the sacrifice of air volume. A hot G4 tower needs air volume, and I would be hesitant to use just any fan, especially less than 65 CFM.
A lower output fan that has high static pressure however, can compensate for lower CFM ratings.

One sure way to reduce noise when using replacement fans is to use the towers fan connectors so that OS X fan kext control allows for variable speed.
Running any fan at 12V will always result is the fan running at its highest speed and producing the most noise.

Another alternative, as in my Sawtooth case mod, is to add a fan and run the case fan (120 mm) at a slower RPM.
The sum of the two fans are greater than the OEM 120 mm fan, but noise was greatly reduced without hurting cooling performance.

Bearings and Blade design

Bearing type and blade design are of major importance in the sound a fan produces.

Bearings are typically ball or sleeve, with the latter having much shorter lifespan than the ball bearing.
Sleeve bearings, though, can be much quieter.

Fluid bearings are a third type, which are very quiet as compared to ball or sleeve.
Service life is better than sleeve, and varies in comparison to ball based on manufacture. 

Blade design is an area continually changing.
The quietest fans will have some blade (and material) design changes from standard fan blade types.

Recommended Fans

120 mm x 120 mm x 25 mm
For Sawtooth, Gigabit Ethernet, Digital Audio and Quicksilver:
Cooler Master R4-L2R-20CK-GP 120 x 120 x 25 mm 
12 Volt, 4.2 Watt, 0.35 Amp 
90 CFM, 2000 RPM, 19 dBA 
Definitely quieter than the OEM fans after the system warms up.
Too low of output for MDD.

120 mm x 120 mm x 38 mm
For MDD:
Silverstone FM-122  120 x 120 x 32 mm 
Scythe Slipstream
Scythe Kamaflex

60 mm x 60 mm x 25 mm

Vantec ThermoFlow TF6025  60 x 60 x 25 mm 
12 Volt, 1.17~1.8 Watt, ? Amp 
9.9~24.2 CFM, 1900~4200 RPM (max), 19~33.5 dBA 
Thermally regulated PWM

This fan is a good choice to replace MDD PSU fans.
It will also work as a replacement for Quicksilver CPU fans.
VGA Coolers

Aftermarket VGA coolers are a good way to increase the cooling efficiency of stock coolers on performance graphics cards.
Quite often along with improved cooling, noise is also reduced.

For some cards, like the Radeon 9800 Pro which have a notoriously weak and short-lived cooler, a third party cooler should be considered as necessary.

If one wishes to over clock a graphics card, improved cooling will increase your chances of success.

Selection of a VGA cooler  always needs to have space taken into consideration.
many coolers encroach on the PCI slot next to the AGP slot, and in the case of the MDD, most can’t be used due to the location of the memory slots next to the AGP slot.

Construction of coolers vary, but all copper construction and inclusion of heat pipes are characteristics of some of the best coolers.
Recommended Fans

If you have a Radeon 9800 series or Geforce 6800 series card, and if you can find one, the best VGA coolers ever made, IMHO, were the Arctic Cooling Silencer series.
 For the Radeon 9800 Pro, the ATI Silencer 1 Rev 2.
 For the Radeon 9800 XT, the ATI Silencer 3.
 For the Radeon X800 XT, the ATI Silencer 5.
 For the Geforce 6800/7800, the Arctic Cooling Silencer NV5 Rev 3.
All Arctic cooling VGA coolers occupy the PCI slot next to the AGP slot.

The Zalman VF700 and VF900 VGA coolers are also excellent coolers.
As with the Arctic Cooling coolers, the PCI slot next to the AGP slot will not be usable, but the graphics card will run much cooler, especially the Radeon 9800 series cards.
I prefer the all copper VF 900Cu coolers, as the heat pipe construction enhances cooling.
Both VF 700 and VF900 coolers are virtually silent.

For MDD users, the AGP slot and memory slot configuration precludes the use of many coolers.
With 9800 series cards in the MDD, the Vantec Iceberq coolers offer increased cooling performance without encroaching on the memory slots next to the AGP slot.


CPU Coolers

Changing a CPU heat sink or adding a cooler isn’t usually necessary, unless you are using a processor from a Quicksilver in an earlier G4, or unless you are using a CPU upgrade that doesn’t have a heat sink, or was meant for a different system like my PowerLogix CPU upgrade is.

If one plays around with over clocking of CPUs, then a better cooler or the addition of a fan is probably best.

Should you find yourself in need of a third party CPU cooler, size restrictions will be a limiting factor in available choices.
There are quite a few low profile coolers

Another major consideration is mounting.
For Apple processors, as well as CPU processor upgrades that use a square heat sink peg pattern, the Intel LGA775/1156/1366 mounting for third party coolers will allow connection to the CPU daughter card.
Use of a copper or aluminum shim of 3 mm thickness will be necessary for contact.
Be sure to apply thermal compound to both sides of the shim.

My CPU Cooler Mod links:

Quicksilver Heatsink Mod for Powerlogix 

Scythe Big Shuriken in a Quicksilver

Other Favorites:

Liquid Cooled MDD

Liquid Cooled Quicksilver