I decided to overclock my i5 3570k to 4.2 which is all fine and well its stable, but for some reason my bus clock changed to 99.77 http://gyazo.com/8c027a4acbd75627990b3787631d6c56 so I checked on my motherboard and it says its set to 100, but how? my motherboard is a Msi-z77a g43
It's not so uncommon to see a little variance. It's not like 99.77 will make a difference from 100.0, but you could always try setting the motherboard to 101(or 100.xx, yeah) and see what that gives you. On the other hand you can also check with other tools, like CPU-Z for instance.
I have the same motherboard. If you really want it back at 100, you either have to reset it to 100 which reads out as 10000 in BIOS, or set it to 10003 or some goofy number like that. I suspect it has something to do with either the power delivery of this mobo, or power/voltage settings. I've messed around with it, but having the clock change like that doesn't bother me anymore.