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ATI 9800 PC to Mac Conversion

G4 Quicksilver Mods

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The main mod, the one which is the source of the need for the other ones!

The
Mystic Room was the first site to show how to overclock the Quicksilver Power Mac. Since I wanted to be able to easily switch between multipliers, I used a DIP switch mounted on a small board with 1 kΩ resistors (same value as the resistors unsoldered from the CPU daughter card). Very useful, and raises the coolness factor tremendously :]

A dash means no resistor present, a R indicates presence of a 1 kΩ resistor.

The rubber band and tape are there to hold the wires, since if they move close to the solders these can break very easily.
Thankfully the picture is a little blurry, so my poor work with the voltage registers isn't too apparent :] These resistors sure are tiny...


While overclocking to 933 MHz was a walk in the park, at 1 GHz an annoying issue appeared: L3 cache was usually not activated at startup, either silently with OS X, or with an alert box with OS 9. At first I suspected the L3 cache chips, but then saw that they were rated for 250 MHz, so that probably wasn't the source of the problem. (These chips are DDR memory, so effective maximum clock rate is 500 MHz; as the 7450 in the Power Mac G4 867 drives the L3 cache at half the processor clock rate, up to 1 GHz the L3 cache isn't overclocked).

I then considered raising the 7450's core voltage. Inspired by Michiro Isobe's article on
Digital Audio Power Macs overclock, I examined the Quicksilver CPU daughter card, found the buck controller (ON Semi CS5165), read its documentation, and obtained the following table:


A dash means no jumper present, a R indicates presence of a 0 Ω
resistor.
Other values require also modifying Vid 3 or Vid 4.

 

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Overclock and voltage tweaks

 

Blow hole

 

Miscellaneous case mods