Monthly Archives: February 2007

Powermac G4 MDD cooling and noise reduction




I have owned an awesome Apple Powermac G4 for about two years now. It’s a 1Ghz with dual processors which is commonly known as the Mirror Drive Door model or MDD for short, due to it’s mirror finished optical drive doors. It has been a faithful servant so far for all sorts of stuff like video editing, music production, photo’s, web surfing, email & business duties to name just a few. I noticed when I first got it that it was a bit noisier than my old G4 533 Powermac, but until my girlfriends mother complained one night that it kept her awake all night, I didn’t really take much notice of it. After that though it started to drive me crazy & I started a long campaign to quieten the thing down.

First thing I did was search google for information of how to do it & I found this page which document in detail how to replace the main 120 mm cooling fan.

Here is a link to Apple’s description of how to replace the 120mm case fan

After trying one fan that just didn’t cool the G4 well enough I found on a website called, a “SilenX” 120x120x38mm – 18dBA – 90CFM which is whisper quiet & cools the mac just as well as the original Delta fan that came from Apple, only it’s about 300% quieter. It made a big difference.

I also read about a software modification to Mac OSX called ” Nap Mode” which to cut a long story short, basically cycles the processors down into a “mini sleep” sort of mode, reducing the temperature and therefore the noise from the fans is quieter without losing any speed. This made a massive difference, but also now made a new noisy high pitched sound from the power supply fans. For G4 MDD owners you must download version 3.5.2 of CHUD, later versions do not work with MDD Powermacs. Some other models of Macs come with Nap mode enabled as standard like the G5 Powermacs & the PowerBook G4, so it’s not a risk to use.

I also created an applescript that I saved as an application & put in my Powermac’s start up items so that nap mode is automatically turned on every time I turn it on. To do this just download the applescript below, unzip it then open up System Preferences – Accounts – Login Items. Then just drag the nap mode applescript into the Login Items Box. Here is the link to my applescript:

An applescript to enable Nap mode

After more research I found that another main source of noise is from the standard power supply fans that come with the MDD G4, so I found the quietest fans on the net to replace them. I chose the fans that come on the Thermaltake Volcano 5 heatsink and fan combination – the Everflow model F126025DH, which spin at 4550rpm with a maximum airflow of 32 CFM and a noise level of 31 dBA. These are actually the same fans as recommended on the above instructions at, so I was confident that they would do the job. The installation is not for the faint hearted so if your not good with electronics & fixing thing’s I wouldn’t attempt it. This made a big difference once again. I also put in a foam insert between the power supply & the case as instructed below.

Finally I put the Powermac down on the floor under my desk which quietened it down again, so after all these measures I now have a Powermac G4 MDD, which is whisper quiet and much more suited to music production.