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Replace fans on cMP 4,1?

D

DougTheImpaler

macrumors 6502a
Original poster
Feb 28, 2006
587
162
Central Illinois
I recently acquired a cMP 4,1 (now flashed to 5,1) and I'm hot-rodding the crap out of it. I was wondering about replacing the fans. There's nothing wrong with them, they're just louder than I like. Particularly the expansion slot fan. It'll crank up to around 2000RPM for (what I can tell) no good reason, and then slow down again, sometimes as low as 800RPM, but usually setting around 1300-1400RPM.

I was wondering if any old PWM 4-pin (92mm?) fan could be plugged into that fan's header, or if I was limited only to Apple's fan. I have taken the fan out and inspected it, it looks like it'll come out of the assembly, though I haven't actually tried.

The other fans all seem fine, so I don't think it's temperature related. The temps in HWMonitor look fine, they don't spin up above the minimum 600RPM (or 800RPM for the one inside the heatsink).
 
Question, what video card do you have in the machine? I had an Apple/ATI 5770 in my 4,1->5,1 until it died and Apple replaced it with a 5870 (vid card was still under warranty!). With the 5770 the PCI fan would start out around 2000rpm then drop to 1200 when I got to the boot screen. I'd have to stress the video card using OpenGL Extension Viewer (in the MAS) which would allow the fan to throttle down to 800rpm (where it should be).

The 5870 starts at around 2000rpms at boot but slows to 800 at the login screen. It's very weird.
 
I have a Radeon 7950 that I flashed to include the EFI ROM. But up until Thursday, it was a GTX 750Ti. The machine exhibits the same behavior with all of them (Radeon without EFI, Radeon with EFI, and GeForce). It also happens with stock firmware for MacPro4,1 and with the 5,1 upgrade.

With the stock card that came with it (GT 120) it doesn't seem to do that. Maybe it really does get warm in there.

For now when I boot I use SMC Fan Control to crank all the fans up to max using a custom profile and then let them spin down with the default one, and it spins down to around 800rpm. Seems to take forever to do it, though. The others all spin down in about 5 seconds. Takes the PCI fan about 60 seconds to get below 1400rpm again.

Doesn't happen in Windows, oddly enough. Still it's kinda funny to see the CPU temp in the 27-28C range when it's idle. :cool:
 
DougTheImpaler said:
I have a Radeon 7950 that I flashed to include the EFI ROM. But up until Thursday, it was a GTX 750Ti. The machine exhibits the same behavior with all of them (Radeon without EFI, Radeon with EFI, and GeForce). It also happens with stock firmware for MacPro4,1 and with the 5,1 upgrade.

With the stock card that came with it (GT 120) it doesn't seem to do that. Maybe it really does get warm in there.

For now when I boot I use SMC Fan Control to crank all the fans up to max using a custom profile and then let them spin down with the default one, and it spins down to around 800rpm. Seems to take forever to do it, though. The others all spin down in about 5 seconds. Takes the PCI fan about 60 seconds to get below 1400rpm again.

Doesn't happen in Windows, oddly enough. Still it's kinda funny to see the CPU temp in the 27-28C range when it's idle. :cool:
Click to expand...

You should read these posts.
https://forums.macrumors.com/posts/18636713/

https://forums.macrumors.com/posts/18636977/
 
DougTheImpaler said:
For now when I boot I use SMC Fan Control to crank all the fans up to max using a custom profile and then let them spin down with the default one, and it spins down to around 800rpm. Seems to take forever to do it, though. The others all spin down in about 5 seconds. Takes the PCI fan about 60 seconds to get below 1400rpm again.
Click to expand...

Same with my iMac. When I set the minimum speed to the max so the fans spin up, then set it back to default, the fans gradually slow down, whereas in my MBP they slow down instantly. However if I use Macs Fan Control to set the actual speed to the minimum, it slows instantly.
 
DougTheImpaler said:
I was wondering about replacing the fans. There's nothing wrong with them, they're just louder than I like. Particularly the expansion slot fan.
Click to expand...

i have pondered this exact same question. i've actually taken an old PCI fan apart from another mac pro. the fan is 92mm, which is a really common fan size. there are roughly 3 problems i saw with it, each of which (i figured) could be overcome.

1) attaching the fan to the fan case. apple used rubber mounts that broke/tore when i pulled it out of the case. one could use a skinny nut and bolt but that may create more vibration leading to noise again. or if we could source the rubber "plugs" or even something similar from somewhere, would provide a much better solution.

2) the fan plug on the mac pro is, of course, proprietary. meaning it's not the same as standard PWM 4 pin plugs. SO, to solve this part, i would say to snip the mac plug, leaving long tails and solder to the [snipped] wires of the new fan. the problem here, is that every wire of the mac fan is black. which wire goes where? how could we find this information? schematics anywhere/one? perhaps an apple tech lurking could clue us into which wire does what?

3) this may just be the 3rd party fan i was looking at (a noctua 92mm) but not only is it MUCH quieter, it also moves less air comparitively. something i could absolutely live with, given my graphic designing/digital painting doesn't ever bump my fans into jet engine mode. but something to consider if your fans DO rev up a lot.

these are a few things i have been thinking about. in fact, i was going to try getting a little more research together and make a post here regarding this topic, asking for help/advice/caution. i would love to do it and perhaps both of us together can feed off each other. i would be more than happy to guinea pig the heck out of this. and, if, in fact, it does work, the power supply fan would be the next one in my sights.
 
s-hatland, I didn't realize it was a proprietary fan connection until I took it out of the system today to remove the processor/fan cage. Whoops. :cool:

I figure the speeds are based on temperature, so if I can figure this out, it won't lead to a warmer case unless the fan is running at its max rated RPMs. Even the bottom fans in the processor cage use some sort of slightly weird connector. Not sure if it's going to wind up being worth my time. For now, starting some sort of fan controller software helps.

poiihy thanks for the tip about Macs Fan control. Hadn't heard of it before, and it does a good job. :)
 
DougTheImpaler said:
I recently acquired a cMP 4,1 (now flashed to 5,1) and I'm hot-rodding the crap out of it. I was wondering about replacing the fans. There's nothing wrong with them, they're just louder than I like.
Click to expand...

This used to drive me NUTS. I am musician/audio professional and at the old place I had the MacPro sitting under my desk. Unbearable.
 
zephonic said:
This used to drive me NUTS. I am musician/audio professional and at the old place I had the MacPro sitting under my desk. Unbearable.
Click to expand...

That's exactly my problem as well. I have a homes studio and I can hear it in my acoustic guitar and vocal recordings. The guitar might peak at around -15 and the fan is there, omnipresent around -60. I've tried using a gate plugin but it seems to lose some nuance.

For now my solution is to download Logic Remote and record in another room. Kinda works.
 
Do not replace the fans in the Mac Pro. These are custom 4-pin Apple fans (manufactured by Delta) that use an analogue 0-12V signal on the forth pin to determine the rotor speed (versus PWM, where it's a digital TTL square wave). If you plug a PWM fan in there, it won't work properly- assuming the fan doesn't fry itself and possibly damage the logic board as well.

Your fan "problems" are caused by a bug in Apple's SMC firmware. There's a good chance that if you load the system down (ie, open iTunes and run the visualizer for a few minutes)- the fan speed will increase until it levels off, then suddenly drops down to ~800-1000 RPM. After that happens, the fan will remain at this speed until the machine is started from a cold start.

If this doesn't work, then it could be that your cross flash is causing some bizarre interaction with other hardware in your machine (probably the GPU). Either way, there's really nothing you can do about it since all the fans are proprietary. You might be able to replace them with a 3-pin fan (GND, +12V, tach)- but then they're going to run at 100% speed all the time and I don't know if the SMC is going to power down your machine because the fan tach readings are incorrect.

-SC
 
DougTheImpaler said:
That's exactly my problem as well. I have a homes studio and I can hear it in my acoustic guitar and vocal recordings. The guitar might peak at around -15 and the fan is there, omnipresent around -60. I've tried using a gate plugin but it seems to lose some nuance.

For now my solution is to download Logic Remote and record in another room. Kinda works.
Click to expand...

We moved house three months ago and in the new place I have built a separating wall in the garage to keep the computer away from the listening environment. I made a 3" cable gutter in the wall and have 10' extension cables for mouse/keyboard (USB), audio interface (FW) and display (DVI).

No more hum. Life is good.

At the old place I did toy with the idea of replacing the fans, but I'm not all that handy with electronics and know just enough to be dangerous, so I decided it was not worth the risk.
 
zephonic said:
We moved house three months ago and in the new place I have built a separating wall in the garage to keep the computer away from the listening environment. I made a 3" cable gutter in the wall and have 10' extension cables for mouse/keyboard (USB), audio interface (FW) and display (DVI).

No more hum. Life is good..
Click to expand...

Yes! A Machine Room makes the studio real. A closet works great, but better feed some AC in there, or close the door only when necessary.
 
ScottishCaptain said:
Do not replace the fans in the Mac Pro. These are custom 4-pin Apple fans (manufactured by Delta) that use an analogue 0-12V signal on the forth pin to determine the rotor speed (versus PWM, where it's a digital TTL square wave). If you plug a PWM fan in there, it won't work properly- assuming the fan doesn't fry itself and possibly damage the logic board as well.
Click to expand...

well that ends that, i guess. didn't even bring an umbrella for this parade.
 
Before you consider replacing the fans (I searched for weeks on this topic myself) try using a can of duster gas and blowing it out first. Every year my MP 4,1 starts accumulating a ton of dust and I always end up Googling fan replacements, only to buy a can of duster, spend about 30 minutes, and everything is quiet (and clean!) again at least for another year or so.

I tried replacing one of the fans with a relatively expenive Noctura and it didn't work, didn't even spin. I had gotten all the wires lined up correctly but as mentioned above, the signals on the Apple fan are different than your average PC ATX fan. I put the original Apple fan back in and no more problems, especially after a good squirting of duster gas.
 
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