The iMac ClockUp page was originally posted at <http://www.bekkoame.ne.jp/~t-imai/imace1.html> and is no longer available there. We have adapted that information for the benefit of those who wish to overclock tray-loading iMacs. The original author is not known to us.

This information does not confirm stable operation. Please note that any modifications you make to your iMac are made at your own risk.

I analyzed how to increase the clock speed of an iMac. If you adjust the set of resistors labeled “R117” to “R124”, which are on the underside of the system module, you can configure the processor clock PLL.

First, you need to take out the logic board assembly and remove the system module from the I/O board.

Next, configure the set of resistors labeled “R117” to “R124” that are on the underside of the system module.

Resistor Settings

CPU Clock	PLL Config	R117	R118	R119	R120	R121	R122	R123	R124	Note
233 MHz	x3.5	x	S	S	S	S	x	x	x	Rev. A & B
266 MHz	x4	x	S	x	S	S	x	S	x	Rev. C
300 MHz	x4.5	S	S	S	x	x	x	x	S
333 MHz	x5	S	S	x	S	x	x	S	x	Rev. D
366 MHz	x5.5	S	x	x	S	x	S	S	x	DANGER!
400 MHz	x6	S	x	S	S	x	S	x	x	DANGER!
433 MHz	x6.5	S	x	S	x	x	S	x	S	DANGER!
466 MHz	x7	x	S	x	x	S	x	S	S	DANGER!
500 MHz	x7.5	S	x	x	x	x	S	S	S	DANGER!
533 MHz	x8	x	x	S	S	S	S	x	x	DANGER!

• S – mount resistor
• x – remove resistor

Keywords: #overclockimacg3 #overclocking

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