Pass the bus of G4 Bi 867 to 167Mhz

par Lionel - 22/06/2003

Or how to make jump the last fastening of Apple

Many thanks to Amber's eyes who compared the 2 computers under a magnifying glass for 2h30, Pimus for lending us a brand new G4 Bi-1GHz and Bakayo for his incredible welding skills.

Here are the modifications needed to change the G4 Bi-867's bus clock from 133 to 167MHz.
You'll note that changing the bus speed to 167MHz would overclock the CPU to over 1GHz. To prevent this, you'll have to change the CPU's multiplier coefficient from x6.5 to x6.

WARNING : for your computer to remain stable, you have to use DDR-SDRAM PC2700 modules. The usual PC2100 modules are not certified for working at these kinds of frequencies.

This is the back of the motherboard, I circled the 3 resistors to look for.
They are labeled R676, R678 and R677.

133MHz - one resistor in each place.
167MHz - take out R676.

There are probably other possibilites but we didn't have time (or suitable DDR modules) to test them out.

Apple added a second protection on its motherboards. If you change these parameters, it will not post at 167MHz unless you use a Bi-1GHz or Bi-1.25GHz daughter board.

Here's the way to circumvent this protection :

On the Daughter Board (see photo), there a group of resistors numbered as following :

	167MHz Bus	133MHz Bus
R27	empty	empty
R22	empty	RESISTOR
R26	RESISTOR	RESISTOR

So this really is another of Apple's locks.

On this screenshot you can see the 167MHz bus. The CPU Card is from a real Bi-1GHz, not an overclock.

For any additional information, please contact amber@noos.fr

WARNING : MacBidouille or its members canoot be held responsible for any hardware degradation or physical, moral and financial prejudice.