Hey all. This is a strange question but something that has been driving me nuts. I have a PM Dual 1.8 and I am pretty sure I have a general idea of what all the internal parts are... except for one. What is that roundish thing behind the hard drive cooling fan? I have attached a pic so you can see what I'm talking about. Does anyone know what that thing does or what it is? Thanks
Got a tip for us?
Let us know
Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
What is this thing?
- Thread starter Chrispy
- Start date
- Sort by reaction score
So does it have moving parts in it? I think mine makes a strange squeak every now and then haha. I have tried stopping all the fans one by one when it does it to pinpoint which fan is making the sound but it seems to be coming from that thing haha. The noise happens on a very very rare basis so it does not really bother me but I was curious. I have Applecare so if I wanted to be a stooge I could have Apple replace it 
Hmm... never noticed that before, but in any case, it's not the speaker--that's to the right of the PCI-zone fan.
After breaking out a flashlight I'm guessing that it's a blower either forcing air down behind the motherboard to keep it cool, or sucking air up from behind it and venting out the back past the drives. It's shaped like a blower, and there's power going to it, and it has what appears to be an inlet or outlet on the back end (behind the hard drives near the top). Plus, there should be 9 fans in my DP, and I can only find 8 (2 on each end of the processors, 2 in the PSU, 1 PCI zone, 1 drive zone) if I don't count it, so unless there's one I'm missing (somewhere in the PSU?) that's what it's got to be.
I can't get past my drives to check if there's any airflow and if so which way it's going, but the fact that there's no dust on the "vent" I can see indicates that it's probably sucking up from below and blowing out the back, if that's what it does at all. That'd make more sense in terms of airflow anyway, as it'd match the direction of the drive zone fan. Either that, or it never runs.
After breaking out a flashlight I'm guessing that it's a blower either forcing air down behind the motherboard to keep it cool, or sucking air up from behind it and venting out the back past the drives. It's shaped like a blower, and there's power going to it, and it has what appears to be an inlet or outlet on the back end (behind the hard drives near the top). Plus, there should be 9 fans in my DP, and I can only find 8 (2 on each end of the processors, 2 in the PSU, 1 PCI zone, 1 drive zone) if I don't count it, so unless there's one I'm missing (somewhere in the PSU?) that's what it's got to be.
I can't get past my drives to check if there's any airflow and if so which way it's going, but the fact that there's no dust on the "vent" I can see indicates that it's probably sucking up from below and blowing out the back, if that's what it does at all. That'd make more sense in terms of airflow anyway, as it'd match the direction of the drive zone fan. Either that, or it never runs.
Well said Makosuke! You gave a very logical explanation for what it very well may be. That would make sense too as I don't hear the squeak all that often. I would guess that fan only comes on to move air out from behind the logicboard every now and then... don't see that on many PCs haha. Apple really thought of everything on these G5s I guess
One more piece of evidence arguing that it's a logic-board-rear cooling blower: I just checked and among the many temperature sensors on my G5 is one specifically for "Main Logic Board Backside". No need to monitor the temp if it isn't cooled...
Blue Velvet said:
Or perhaps some kind of hypnotic control emitter which converts people into Mac fanboys?
Apple likes putting temperature sensors for everything, for instance on my ibbok there is a temperature sensor for the battery, memory, gpu, and the processor.Makosuke said:
Also, i think it was Hardware Monitor where when you look at the list of fans it lists one as a blower.