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Overclocking Your Vintage Mac

Overclocking the Mac LC Series

LEM Staff - 2014.09.16

Only two Mac LC models can be overclocked to improve performance. The LC II and LC III can be chipped; the original LC and LC III+ cannot be overclocked. You can also upgrade LC models using third-party accelerators the plug into the LC processor direct slot (PDS), which will bring more performance at a higher price – and may be difficult to find after all these years.

Many Mac models can be “chipped” to run at a higher speed. These pages provide information on the maximum reliable speed. This may vary from one machine to the next. Chipping is not authorized by Apple. Any modifications you perform on your Mac may damage it and will void any warranty. Modifications are done at your own risk.

Be sure to visit The Clock Chipping Home Page, the definitive resource on chipping the Mac.

Macintosh LCLC II and Performa 400-430

The LC II is not normally shippable, but Ed Nye shares his technique for overclocking it and says that graphics and real life performance increases dramatically.

See Clocking the LC II / Performa 400 through 430 for details.

LC III and Performa 450

This modification will run an LC III or Performa 450 at 33 MHz. This makes it identical to an LC III+ and Performa 460. Before you perform the modification, you will need one of the following or the machine will not boot once it has been clock chipped:

  • The latest version of System Enabler 308.
  • Version 1.1 of System Enabler 003
  • System 7.5

The modification:

  1. Remove the resistor in position R14 (0 ohm). It is located at the top of the motherboard, near the RAM slot.
  2. Install the resistor you just removed into position R74.

A few notes:

  • The computer will now identify itself as a Mac, not an LC III. Also, the Gestalt ID will change from 27 to 62, the same as an LC III+ and Performa 460. This will not cause any problems with this machine.
  • According to MicroMac, the Diimo 128k L2 cache card for the LC III and Performa 450 will not work in the LCIII+ or Performa 460. This means that the Diimo 128k L2 cache card will also not work in a clock chipped LCIII or Performa 450.

Info from LCIII (P450) Speedup

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