G3 in a G4 (Mad Science Project Thread)

[Astal]

Well I did a small project here... I started with my G4 DA 466 board with a 7400 on it. I removed the CPU and I cleaned the pads...

I got in a PowerPC 750S yesterday night, so I decided to work on getting that installed on the G4 board

Everything looks great! I install the board and nothing happens. I forgot to adjust Vcore, I come back and I install the CPU board again with the proper VCore (was 1.8 for the G4, needed to be 2.1 for the G3), and the CPU gets warm! But no bong.

Very disappointed to report that at this stage you cannot run a G3 in a G4.

So why did I do this? Because I can...

I'll be trying a firmware patch soon when I get a new CPU board for this with a G4 so it can boot, then retry the G3. If anyone has ideas I'd be glad to hear them!

Edit: someone on the TinkerDifferent Discord just came up with why it probably isn't working! 133MHz FSB models use MPX for north bridge communication and well, G3s don't have that! I'll need to find a Sawtooth/GigEth!

 

[3lectr1c]

Don’t show this to @Action Retro…

It would be his worst nightmare!

 

[Astal]

Don’t show this to @Action Retro…

It would be his worst nightmare!

Ha. @Action Retro, want some weird Mac shit!

 

[Astal]

It would appear all AGP G4s use MPX (labelled as MaxBus), so the dreams of an AGP G3 are dead.

Very disappointed.

Next up: 604e PowerBook

 

[Nixontheknight]

It would appear all AGP G4s use MPX (labelled as MaxBus), so the dreams of an AGP G3 are dead.

Very disappointed.

Next up: 604e PowerBook

but there's nothing stopping you from putting a G3 processor card on a G4 yikes

 

[Astal]

but there's nothing stopping you from putting a G3 processor card on a G4 yikes

Yeah, but that's just a B&W! I wanted an AGP G3 for no good reason.

 

[Astal]

Undone, and ready for a 7410 upgrade. Sad the experiment didn't work, but I'll install a 500MHz 7410 and just use it that way sadly.

 

[Nixontheknight]

Yeah, but that's just a B&W! I wanted an AGP G3 for no good reason.

but the case would make it a G3 Graphite

 

[Astal]

but the case would make it a G3 Graphite

Interesting thought...

 

[Astal]

I have tried again with a reballed G3, it's on there and looks about perfect. Apparently the last PowerBook G3s use a uninorth chipset, so there might be a way to actually get it running... I'm going all the way and is there a way to patch OF to boot with an unknown CPU?

Edit: It does turn on and just sits there, nothing else, with the iBook when it didn't like the CPU it would start to boot/spin up the fans, then immediately shut down when it didn't like the new CPU. So it might just be a UniNorth incompatibility.