[RJGill842]

I have a dual 1.25ghz PowerMac G4 ( Mirrored Drive Doors) with 2.5gb RAM. I recently purchased a 512mb video card and was worried about the extra heat generated by the GPU (which has its own fan), so I decided to purchase a PCI slot fan. The one I bought is made by Antec (a very well known manufacturer) and is actually the size of two PCI slots - its a very large fan that moves ALOT of air. However, the standard (and extremely large) fan that cools the CPUs runs at full speed (it's multi-speed) constantly. It makes no sense to me, the machine certainly can't be HOTTER, can it? If I unplug the new fan, the CPU fan runs at its normal speed. Is this normal, what could be causing this, and am I somehow making things hotter? I'm no computer novice...but this is a stumper! Any help would certainly be appreciated! Thank you! - RJGill

[seanc]

Which fan is the CPU fan? The one in the case opposite the CPUs? It could be your big pci slot fan is blocking it.

[RJGill842]

Yes, it's directly opposite the CPU - but inside the case itself. The MDD machine's CPU fan doesn't actually vent or pull air directly outside of the case, it sits in the middle of the case. The two fans are not close to each other at all. I'm wondering if the fact that the new fan isn't automatically adjustable and controllable by the machine like the other fans, maybe everything defaults to max speed because the new fan runs at max speed? Perhaps since the machine can't control that one fan, everything is set to max. Just a thought.

The fan IS speed adjustable, but via a switch for Low, Medium, and High - it can't be controlled via the machine itself. I suppose it doesn't matter that the fans are on high all the time, it will just keep things cooler. It's EXTREMELY LOUD tho...but I don't mind, shows power

[DrBoar]

For the CPU fan to work the airflow has to pass through the CPu heatsink. A very powerful PCI fan such up the air and might actually decrease the flow past the CPU heatsink

I have removed the loudspeaker and made a cardbord baffle to get the powersupply to suck in cool air from outside instead of warm air from the inside.

[RJGill842]

Thats kinda what I was thinking actually - because I recently noticed that the fan speeds were changing again. It is a fairly powerful PCI fan...the most powerful I've ever come across...and you may be right. I cannot understand why they decided to go with this setup for the already hot Dual G4s. I have an 800mhz G4 also, and its cooling seems better designed - it blows cool air from the outside across the fins, rather than warm case air. Wonder why they redesigned it this way?

Also - I'd like to monitor the heat inside of the machine (ambient) as well as on the CPUs. I know this is very easy with a Windows machine...but I haven't found anything for OS X (10.4.7) that will allow me to have real-time readings of fan speeds and temps. I'm sure that one exists, any help would be greatly appreciated! -RJGill

[DrBoar]

Go to versiontracker.com and download Temperature Monitor. The dual G4 does not have any fan sensor that programs can detect.

It has worked better for me with a HD cooler. (http://www.xpcgear.com/hdfan350.html) I installed in the HD bay that is alongside the CPU heatsink. I flipped the fans over so they blow air toward the heatsink. The idea was that the combined airflow would force more of the airflow deeper into the heatsink to better cool of the CPU. It lowered the CPU temp by 4C or so.

The PCI fan can be slowed down by running it with 5 or 7 V instead of 12. The original PCI covers are perforated, if you use solid ones, the function of the PCI fan will improve.