Loud G5 fans related to Geforce 7800GT?

[Greene]

Hey everyone - recently got a DC 2.3 G5 with a 7800GT (!!). Haven't had much time to play with it, but threw Leopard and Tiger on it this weekend and noticed 2 things:

• I love these machines.
• The fans on this thing are ridiculously loud - even compared to my 2003 G5 (and seemingly louder than the 2.7 I sold)

I checked out iStat, and the problem seems to be that my backside, expansion slot, and drive bay fans are stuck at a constant rpm and creating the noise. Tried the ASD and Thermal Calibration tools - no failures, no issues, but these fans still loud / stuck at the same values.

My question: Is this related to the 7800GT? It doesn't seem like it's running hot, but then again I'm not sure what a baseline would be here. Maybe somebody who has more experience with high end graphics cards of this era can help me out.

 

[bunnspecial]

I've run late G5s with almost every BTO/retail video card including a couple of 7800GTs.

In my experience, the card is not appreciably noisy, and I don't really notice it over the rest of the G5 fans.

One thing I will mention is that shortly after buying my first 6800 Ultra, I took it apart to clean and repaste it. On reassembly, I forgot to reconnect the heatsink fan. Within a few minutes of startup, the PCI fans would be running at full blast, but I also observed an very alarming increase in GPU temperature(it hit 110ºC at one point) and assume that the computer was running the fans it directly controlled to counteract this.

Assuming the fan is working alright, it might be worth your time to take everything apart and clean it-both on the card itself and in the PCI cage area. Dust can not only reduce airflow but can also make what air is flowing more noisy.

 

[Greene]

I took the G5 apart and cleaned it how I could - Overall it was very clean and well cared for. All fans are functioning, what I did notice is that the 6 pin pcie power wasn't plugged in to the board (no cable was included either). Unsure if it was needed on the computer, but I've ordered a replacement and hopefully that will fix the issue

 

[havokalien]

If the card has a plug and its not there It needs the extra power. Also after you do that if the fans on the G5 are acting differently then use AHT 2.5.8 and use it to re calibrate the sensors. You do this when replacing processors (when they die and need replaced)and such.

 

[Greene]

Yeah that was my thought Havokalien - I was a little curious as to why the card worked at all prior to the cable.

Unfortunately though, that doesn't seem to have been the issue. Added the power cable in, calibrated the fans with the ASD (my version of the AHT doesn't have thermal cal (I think)), but still getting those three fans stuck at a constant speed. no errors on the ASD

A couple hypotheses-

• Could be a graphics card issue. I'm about to run an openmark bench and compare it to the scores from other 7800gts (if this data can be found). I have seen some weird artifacting happening during boot screens, where large text flashes briefly on the screen at odd angles.
• Sensors have gone bad in a way that Apple's service diagnostic is unable to detect - seems unlikely.
• Fans are going bad - its possible that all the fans went bad and only the cpu fan/s were replaced.

Update: Graphics Card benches at an appropriate speed (good?)

 

[havokalien]

I would guess maybe its a flashed PC card? If so it may not work well with the fans.

 

[Greene]

Not sure, but i believe its a genuine mac card. I'm not the original owner, but the machine came with Apple-produced documentation about the 7800 card. My guess now is that something's funky with the fans or fan controller.

If the fans from an 03 G5 are compatible, I'll swap them out and see if that fixes the issue.

 

[MacCubed]

Since thermal calibration failed, try running it with a floor fan infront of the G5. My Quad did the same thing, but passed with the fan.

 

[bunnspecial]

Not sure, but i believe its a genuine mac card. I'm not the original owner, but the machine came with Apple-produced documentation about the 7800 card. My guess now is that something's funky with the fans or fan controller.

A couple of things:

1. First, this isn't 100% reliable, but check the gray sticker at the bottom of where the door attaches to the case. If it shipped with a 7800GT, it will be listed there. Of course, the card could always have been added later, but if it shipped with one then it's probably an Apple card.

2. The OEM Apple card is a full-length card card with an extra added section of PC board and metal bracing to engage the anchor slots in the G5.

 

[Greene]

Since thermal calibration failed...

Maybe I miss typed, the thermal cal and all tests in the service diagnostic passed. The fans are still stuck at their speeds though.

A couple of things:

1. First, this isn't 100% reliable...

2. The OEM Apple card is a full-length card card with an extra added section of PC board and metal bracing to engage the anchor slots in the G5.

The card is an Apple OEM card then, it has the same extra section of PCB. Funnily enough, the label says this mac shipped with a 6800. I have the OEM documentation for the card and the seller was a company that used this computer as a graphics station in the mid 2000s, so I could see some graphics cards getting swapped around.

Funnily enough I took a risk and stumbled into a quad which should be arriving shortly. If there isnt coolant coating the MB, I'll have a chance to try this card in another machine and see if the problem persists.

 

[Greene]

Feeling pretty dumb right now...

Turns out the speed of these fans is a function of power draw, presumably from the PCIe slot, and not temperature. The 7800 eats a ton of power. Hence the high fan speeds, which are actually on par for what I'm seeing on other G5/7800 setups.

As far as the noise, well, everything looks clean, and none of the fans sound like they're dying.

So the issue? I haven't used a G5 with this nice of a graphics card / heavy power draw before, and I'm spoiled by the fans on my work rMBP and personal Mac Pro.

 

[pc297]

Btw, if the GF 7800 GT fans are running fast under Leopard, there is a simple resistor mod:

Worked like a charm for me back when I upgraded from Tiger (under which fan revs were fine)