I built a system with a P8Z68-V PRO and Core i5-2500K yesterday. After building it, I entered the BIOS menu and Loaded Optimized Defaults.
I then had an issue with the system powering on/off multiple times each time it was turned on from a cold start. It would say boot up and say "Overclock Failed". It turns out the "Optimized Defaults" were applying an overclock: BCLK set to 104, and multiplier set to 42. Not sure why the defaults were doing this, but I just left it alone for the moment.
I then installed Windows 7 and downloaded the latest 0501 BIOS. I went into the BIOS menu and updated the BIOS. The system continued doing the multiple reboots. After updating the BIOS, I manually set the BCLK to 100, and multiplier to 34, and the system now boots successfully.
So I think I made a couple of mistakes:
* I downloaded and updated the BIOS while the system was not completely stable
* I did not reset the CMOS before updating the BIOS, as I have read is recommended by a few forum posts.
A couple of questions:
1) Have I messed up my system? Should I reupdate the BIOS?
2) How would I know if a BIOS update failed? Would it be pretty obvious that there were problems with the system?
These issues seem to be pretty common nowadays with every SB build. Seems like an inherent chipset issue. There's nothing you have done wrong mostly. If the problems persist then try turning off turbo and try again.
If the BIOS update failed it wouldn't get very far in booting up. As for why "optimized defaults" is using 104 base clock I couldn't tell you, but I'd say just set everthing to where it's supposed to be manually including RAM speed and timings. Also if possible you should set the multiplier to AUTO so that turbo boost works.
Other than that, I've never reset the CMOS before a BIOS update, and as for system stability, well yeah that could cause a bad BIOS update but it would pretty much have to crash during the update.