6 Replies Latest reply: Dec 31, 2012 6:28 AM by PowerPC_Fan
PowerPC_Fan Level 1 (0 points)

I have a G4 MDD dual 1.42ghz and would very much like to overclock it to 1.67ghz. I've read several places that it can be done but needs a voltage increase and lots of extra cooling. All of that is fine but I was wondering if anyone out there has attempted this particular overclock and what success you had?

If I did this what would the voltage setting need to be upped to?


Any and all info on this would be much appreciated.  Also, I realize this could totally waste my board but I'm willing to risk it if I can get the right specifics on the "proper" way of going about it.


Many thanks in advance.

PowerMac, Mac OS X (10.4.11), G4 MDD dual 1.42
  • japamac Level 7 (24,390 points)

    Anyone that I know that has tried it got a few seconds to a few minutes before the chip fried.

    Most have zero stabiity so don't burn up.


    Up voltage to 1.60V or 1.65V when going over 1.58 GHz.

  • LordZedd Level 1 (70 points)

    1.42GHz is as high as the chip can run at. If you want faster you need to upgrade the CPUs to aftermarket 1.6 or 1.8GHz upgrade cards, they use newer generation CPUs that are capable of running the higher speeds safely.

    But, thats a complete waste of money, you could buy a G5 that is better in every possible way for the same money.


    In other words, don't bother messing with your G4. Sell it to somebody that can use it and buy a Dual CPU/core G5.

  • PowerPC_Fan Level 1 (0 points)

    Thanks, japamac, I appreciate you being straight forward about it.  You mentioned using voltage at "1.60V or 1.65V when going over 1.58 GHz", does that mean clocking to 1.58 is stable, or will that fry it as well?

  • japamac Level 7 (24,390 points)

    Stability varies with chip quality. The 1.42 chips were of the better quality within the yield, and many of those allowed easy OC to 1.5 GHz (think GigaDesigns) and some chips even to 1.58 GHz without a voltage mod.


    The trouble with the 1.58 GHz (and faster) clocks is that they greatly shorten the chips life, tend to have stability issues, but, most assuredly, require more intensive cooling methods.

    Complicating this is the difficulty to increase cooling efficiency or use aftermarket coolers in the MDD case.


    Moving the guts to an ATX case or a G5 case allows easier cooling mods to accomodate the heat from OC efforts.


    All OC efforts are a YMMV scenario because of the variables involved.


    If you must, up the cooling and do a conservative OC to 1.5 GHz. That's plenty fast and has proven stable for many an OC'er.

  • LordZedd Level 1 (70 points)

    None are stable.

  • PowerPC_Fan Level 1 (0 points)

    Thanks again, much appreciated.