[ MAC CRYSTAL OSCILLATOR SPEEDUP ] First some disclaimers from PowerPC News: Modifying your Macintosh in any of the ways below will certainly void your machine's warrantee. In addition you will be driving your machine's processor faster than Apple designed it to go, and therefore the possibility of long-term damage to the machine does exist. PowerPC News can not recommend that you modify your Macintosh and we are providing this information on an as-is basis and cannot be responsible if the result is a non-functional machine, or indeed a sticky smoking blob in the middle of your desk. The following
file is republished from the ftp site sumex.stanford.edu where it is maintained by Marc Schrier and we are not responsible for its content. A little background:
All computers operate at a certain frequency with which operations are performed. Within a certain class of computers, for example Mac's with a 68030 processor, the higher the frequency, the higher frequency of operations processed, and the faster the computer provided there is no other speed effecting hardware like a cache or slow data path. The designer of the computer, Apple in this case, will use components that are rated at the same frequency or faster than the final computer will be. The 68030's are made by Motorola. All 68030's are generally alike in what they do, but they are not alike in how fast they can do it. Motorola sells several 68030 processors rated at 16, 20, 25, 33, 40 and 50MHz for Mac's, accelerators and such. A large frequency difference
will require a different mask during production of the processor, but small changes may not. Motorola only needs to guarantee that the chip
they mark as 20MHz will function properly at 20MHz under a variety of conditions. Some chip vendors will test parts at different frequencies
and sort the chips accordingly while others may just label the them at will and sell the chips at the different price as long as they are
within spec. So it is possible that the 20 and 25's actually come from the same batch, are separated on demand, and tested to make sure they
will withstand that frequency. Because of this, it is possible that a 20MHz processor will function fine at a higher frequency, say 25MHz.
Running it faster will however generate more heat.