Author Topic: Mac Mini G4 Overclock just because its fun.  (Read 653 times)

Offline domii

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Mac Mini G4 Overclock just because its fun.
« on: February 27, 2022, 03:55:23 PM »
I know this has been covered before in an old thread, but thought I would start a new one as parts where incomplete.
And it is always a struggle to find the multiplier settings when you need them when many of the old sites have disappeared.

So will post what I have and edit this in future if I make any better progress. Feel free to add anything that would help.
And it is fun - 1.8GHz puts out benchmark numbers over 1000 for geekbench, thats MDD territory.
MacOS 9.22 is ridiculously quick.  Will be posting some Unreal Tournament and Quake fps numbers shortly.

On the backside the resistors R355, R351, R358, R362, Essentially removing them all gives you 1.5GHz
Which should be possible on all the models.

R52 - next to cpu under the heatsink. R52 is important as it provides values above 1.58GHz

You can even use a lead pencil or one of those conductive pens to bridge the pins - providing speeds from 1.67 up to 2GHz.
(there is a 1.92GHz setting with evengthing bridged, not sure if anyone has tried that one, but I would like too in near future)

Some things I found on other threads.
1.25 -> (1.42 safe) or 1.5GHz
1.42 -> (1.5GHz safe) or 1.58/1.67GHz, there is even a chap on youtube with a video claiming 2.0GHz with a massive heatsink.

Late model versions
1.3 -> (1.58GHz safe) or 1.67/1.75GHz
1.5 -> (1.67/1.75 safe) or 1.8GHz

* Obviously replace the heatsink pad/paste with something decent when you do the mods to help with the thermals.
* Also a good time to replace the battery and give it a could cleaning/blasting with air.
* And upgrade the hard drive if you havent already to a mSata SSD using one of those adapters.

The main drawback is heat & voltage. I haven't figured out how to adjust the voltage.
It seems the cpu will go to 1.8GHz with the stock blower and Aluminum heatsink. Which is not horrible, they are well designed for the tiny space.

But I would like to go copper as it would most likely provide up to 50% better heat dissipation on something this small.
After which I might give the 1.92 & 2GHz speeds a go.  (which is silly speeds)

Took some measurements and pictures.

Stock aluminum finned heatsink. 40mmx50mmx20mm.
The Cpu pushpin mounts, 35mm spacing between posts. (or 49mm on the diagonal).
60x60x15mm, 12v 2pin blower flan.

I could probably cut/hacksaw a heatsink smaller and drill the holes if needbe, just need to find something suitable out there.
Might replace the blower as well if there is something more silent. Noctua has good stuff but not sure if they have a 60mm blower. There does seem to be various generics on Amazon - not sure if any are better than stock though.

* I know dosdude1 is doing a full on 7447B chip replacement that rocks 2GHz nicely.
* There was a chap that wired dip switches to the resistors and figured out many of the settings on a thread somewhere. Booted his 1.33 mini all the way to 1.92GHz.
« Last Edit: February 27, 2022, 04:38:26 PM by domii »

Offline FBz

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Re: Mac Mini G4 Overclock
« Reply #1 on: February 27, 2022, 04:07:31 PM »
Impressive!

Especially for all you speed demons out there. ;)

Offline teroyk

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Re: Mac Mini G4 Overclock just because its fun.
« Reply #2 on: March 01, 2022, 02:23:04 AM »
I just think: How about underclocking to 1.00 Ghz with big copper heatsink...fanless solution possible?
I bought my first new Mac when OS X 10.1 released. And I bought that Mac because it had Mac OS 9 too. And I bought my first 68k Mac when Apple stopped PPC Macs.

 


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