Hi, i see from another of your posts that you have just moved over from the dark side. Welcome.
I assume you have a Mac Mini and are feeling the need for speed and have plenty of money to spend.
It is certainly possible to increase the speed of the Mac Mini up to 1.58Ghz but 1.42Ghz seems to be the more stable speed.
Usually, to increase the speed of a processor (overclock) you increase the amount of power it receives. For example, if the processor is receiving 3.0V and running at 1.0Ghz, theoretically the same processor receiving 3.5V would run much faster. Note the use of the word theoretically. Processor manufacturers certify their chips to run at a certain speed. Some processors on the same wafer will happily run at 1.5Ghz, some at 1.4Ghz, some at 1.25Ghz and some, not at all.
So if your chip has been certified to run at 1.25Ghz and you increase the voltage in an effort to increase the speed, it "might" work or it might "burn up". Usually the processor becomes unstable after a certain speed. So you start from the bottom and work up.
Remember, whichever way you go, once you start messing with the resistors that control the voltage, the machine belongs to YOU. The warranty is VOID, totally. If you ever have ANY problem with your machine, you are on your own.
Is it ok for your computer? If you have lots of money and are confident in your soldering abilities, maybe.
Does it improve performance? If it works, yes, if it doesn't, and there is no guarantee that it will, NO. you just got yourself a $500 paperweight.
So, having said all of the above, here is a link that will explain exactly how to turn your machine into the aforementioned $500 paperweight.
I would be interested in how you get on with the modifications
What is that? Does it improve performance? And is it okay for your computer? Someone mentioned the mac mini can be overclocked to 1.58 ghz. I'm wondering how can I do that if it's safe.