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ATI 9800 PC to Mac Conversion

G4 Quicksilver Mods

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Long story short: my overclocked Motorola 7450 CPU had heat problems, and the only solution, save in winter, was to run the Power Mac G4 with the case open, which is inelegant, takes three times the space, opens the door wide open for dust, and can be dangerous for the computer when eating or drinking next to the Mac (spilled orange juice on powered-on motherboards can be fun, but not on mine :).
Replacing fans with more efficient ones wasn't enough; the Quicksilver case's design isn't suited for evacuating lots of heat. So a kind of common mod performed on PC cases, the infamous blow hole, was in order.
(Amazingly, the well known Mac hardware hacker Tycho wrote an article on this subject at the same time I started doing this mod:
Cooling Tech and Theory)


Take an innocent looking Quicksilver Power Mac:
 

What's this on top of the case?

Why, a blow hole of course!

For those wondering why the fan isn't inside the case, it's simply because there's no room since the power supply is only 1 cm below the top panel. There is enough room if installing the fan at the front of the case, on top of the optical drive, but I preferred to mount it just above the heat sink.


Another shot of the blow hole:

I advise to reverse the case fan. In the stock configuration, it extracts air from the case. With the blow hole already doing this, and more efficiently, it's actually better to have the case fan bring fresh air inside. Refer to Tycho's article for the gory details.


So does it work? Yes indeed! I can now close the case while letting the 7450 run at 1 GHz (instead of 867 MHz), imagine that :)

One drawback: additional noise. Not because of the fan, which is actually quite silent (24 dBA), but because of resonance in the case. I'll try to work on it...

Long overdue update: Unfortunately when came summer, I had to back down to 933 MHz because of the heat... So the blow hole gave me a few more months of gigahertz operation, but not twelve months.

 

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Overclock and voltage tweaks

 

Blow hole

 

Miscellaneous case mods