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Beefed-up G3 MT - will it overheat one day?
Posted by: Coloruser on 2025-08-18 06:28:24
I recently pretty beefed up my beige G3 MT

- 768mb/ram
- Radeon 7000 - 32mb
- USB Card
- Sonnet Encore G4/1000
- Adaptec SATA Card with Kingston SATA SSD

Looking at the internals, the Sonnet Encore is huge and cable routing is a bit of a mess. I am running the unit oben on my bench at the moment cause there is not much clearance above the CPU and it's two fans and I first want to make sure, the system runs stable. Using my IR temp meter, the CPU heat sink has a hot spot of 40°C or 104 Fahrenheit. I have a Fairchild VRM and that also stays quite chill at 31°C or 90 Fahrenheit. The Radeon 7000 also doesn't exceed 40°C / 104 Fahrenheit.

So no worries here, but give the fact that the G3 MT only uses the PSU Fan to blow air out of the case, I will have an eye on it. Fortunately, the CPU fan sits right below the internal case fan, that sucks hot air out of the mainboard area.
Posted by: finkmac on 2025-08-18 06:30:09
maybe? maybe not?

i'd maybe add another fan.
Posted by: croissantking on 2025-08-18 12:55:43
I have a Fairchild VRM and that also stays quite chill at 31°C or 90 Fahrenheit.
What does the Fairchild VRM look like?
Posted by: Verdant on 2025-08-18 18:06:33
I recently pretty beefed up my beige G3 MT

- 768mb/ram
- Radeon 7000 - 32mb
- USB Card
- Sonnet Encore G4/1000
- Adaptec SATA Card with Kingston SATA SSD

Looking at the internals, the Sonnet Encore is huge and cable routing is a bit of a mess. I am running the unit oben on my bench at the moment cause there is not much clearance above the CPU and it's two fans and I first want to make sure, the system runs stable. Using my IR temp meter, the CPU heat sink has a hot spot of 40°C or 104 Fahrenheit. I have a Fairchild VRM and that also stays quite chill at 31°C or 90 Fahrenheit. The Radeon 7000 also doesn't exceed 40°C / 104 Fahrenheit.

So no worries here, but give the fact that the G3 MT only uses the PSU Fan to blow air out of the case, I will have an eye on it. Fortunately, the CPU fan sits right below the internal case fan, that sucks hot air out of the mainboard area.

It might be useful to remove the upgrades and get some baseline temperature numbers for comparison.

Also, a PCI slot cooler fan might be a cheap and easy way to improve cooling. Not to mention checking the thermal paste on the CPU - given their age, a refresh with new higher-performance paste may buy you a few degrees of cooling.

What does the Fairchild VRM look like?

Presumably it is labeled as such? Seems that Sonnet found an issue with one of the other manufacturers of the G3's VRM...
Posted by: croissantking on 2025-08-19 00:17:21
Presumably it is labeled as such? Seems that Sonnet found an issue with one of the other manufacturers of the G3's VRM...

There are pictures online of Raytheon, Switch Power and the infamous Royal VRMs, but I’ve honestly never seen a Fairchild. Just curious.
Posted by: Byrd on 2025-08-19 02:07:10
If it's not crashing under load it's adequate and max 40 degrees is well under this. If you can on any vintage Mac a modern fan here and there can help things along markedly.
Posted by: Coloruser on 2025-08-19 03:04:16
There are pictures online of Raytheon, Switch Power and the infamous Royal VRMs, but I’ve honestly never seen a Fairchild. Just curious.
Here we go - using a Raytheon RC5051M Power Management IC.
Posted by: Coloruser on 2025-08-19 03:21:42
If it's not crashing under load it's adequate and max 40 degrees is well under this. If you can on any vintage Mac a modern fan here and there can help things along markedly.
I am thinking of adding a 60mm fan in the baffle handle as Apple has designed two fan spaces there. In the Service Source for the G3 Server/MT, installation is optional for some PCI cards. It will not help in the cramped around the CPU and ram, but it can suck air just thru the vents on the side panel - leaving it to the main fan to push air from the logic board area to the PSU and the PSU fan to push it out of the enclosure.
Posted by: croissantking on 2025-08-19 03:32:22
Here we go - using a Raytheon RC5051M Power Management IC.

Interesting - the Fairchild appears to be just a rebranded Raytheon:

IMG_5644.jpegIMG_5645.jpeg
Posted by: Coloruser on 2025-08-19 03:35:32
Interesting - the Fairchild appears to be just a rebranded Raytheon:
Indeed, interesting. It's just the sticker on the connector and the silk screening on the backside of the PCP that sets them apart
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