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xkola12345x

macrumors newbie
Original poster
May 27, 2021
4
0
Hello,
some time ago I posted about my Power Mac G3 (B&W), which appeared to have a broken motherboard. I unfortunately wasn't able to repair it. That leaves me with a non-functional G3 and not a lot of options. I could buy a replacement board or another G3, but those are getting more rare and more expensive, so I thought of replacing the G3 board with one from Power Mac G4, as they are more common.
My question is, what is the latest model of Power Mac G4, where its motherboard would be a drop in replacement?
I know PCI G4 (Yikes) motherboards are the same as G3, but I would prefer to make it faster.
Am I limited to Yikes, or maybe any Graphite G4 will do?
And what about Quicksilver G4 motherboard?
The first ones (digital audio, not MDD) had a pretty similar case construction to both B&W G3 and Graphite G4, were their motherboards also the same shape and size?
 

Raging Dufus

macrumors 6502a
Aug 2, 2018
614
1,126
Kansas USA
Hello,
some time ago I posted about my Power Mac G3 (B&W), which appeared to have a broken motherboard. I unfortunately wasn't able to repair it. That leaves me with a non-functional G3 and not a lot of options. I could buy a replacement board or another G3, but those are getting more rare and more expensive, so I thought of replacing the G3 board with one from Power Mac G4, as they are more common.
My question is, what is the latest model of Power Mac G4, where its motherboard would be a drop in replacement?
I know PCI G4 (Yikes) motherboards are the same as G3, but I would prefer to make it faster.
Am I limited to Yikes, or maybe any Graphite G4 will do?
And what about Quicksilver G4 motherboard?
The first ones (digital audio, not MDD) had a pretty similar case construction to both B&W G3 and Graphite G4, were their motherboards also the same shape and size?
A board from a Yikes! or Sawtooth would be compatible with your power system, as they all share the same pinout scheme for the PSU, and run from similarly specced PSUs. You can't go beyond the Sawtooth, i.e. you can't use a Gigabit Ethernet (a.k.a. Mystic), Digital Audio, or Quicksilver board without replacing the PSU, because: (1) the PSU in your B&W is not high enough wattage to reliably run a GigE, DA, or QS board; (2) the PSU in your B&W is not pin-compatible with those models. You could change (2) by rewiring an ATX extension cable to match the power inputs on the GigE, DA, or QS boards, but - see (1). You just don't have enough juice.

So, unless you're going to swap out the PSU too, you're limited to B&W, Yikes!, or Sawtooth boards. The Sawtooth, though, will require a bit of modification to the back case to accommodate the different positioning of the audio out and modem ports. See the differences below:

B&W G3.jpeg

Sawtooth.jpeg
 

mustagcoupe

macrumors regular
Jun 6, 2020
141
136

xkola12345x

macrumors newbie
Original poster
May 27, 2021
4
0
Here is an ebay link to replacement rev B motherboards if you want to keep it as a g3. I found out about them from this thread at os9lives (http://macos9lives.com/smforum/index.php/topic,6191.0.html).

The board form ebay would be perfect, if it had international shipping, as I don't live in the US, so it's a no-go.

As for swapping the PSU, I think I wouldn't mind, as I would likely buy a working quicksilver, but with a beaten up case, so gutting it for parts doesn't feel wrong.
And weren't the backplates removable? I'm pretty certain I unscrewed it while cleaning the case of the G3.
 

ADunsmuir

Contributor
Mar 26, 2020
29
31
The board form ebay would be perfect, if it had international shipping, as I don't live in the US, so it's a no-go.

As for swapping the PSU, I think I wouldn't mind, as I would likely buy a working quicksilver, but with a beaten up case, so gutting it for parts doesn't feel wrong.
And weren't the backplates removable? I'm pretty certain I unscrewed it while cleaning the case of the G3.
I’ve had good results asking US sellers if they would ship directly, or via the eBay Global Shipping Centre.
 
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