The "double boots" are a well known phenomenae.
I have had it going back to P965 mobo
It is basically a "reset" - you have done something that a bios/CPU/O/S cannot deal with, so it tries again under a "reset" condition.
The causes are many and also well known
Foremost is not enabling any spread spectrum option (some Z68 have 2). Further aggravated by bios changes that alter whether "auto" means disabled or enabled. You must always select enabled.
Not enabling XMP option for RAM is another. If it has it (some have 2 profiles) - use it.
Any BCLK other than 100.0 - not 103.0 or 100.3
Changing C-states under ceratain conditions
The ASUS AI Suite is another system wrecker, dont even think about using any but the latest. Looks sexy/nice features/fan controls, but I refuse to use it.
Wireless routers, if you have this issue, use another brand or wired.
PLL overvoltage on or off is critical option - this has also been changing with bios versions
Many SSD's have detection issues on Intel controller (think OCZ)
Non XMP RAM should be set manually to CPUID SPD page settings exactly
Full CMOS clear (PSU unplugged and bat out, 30 min)
Overly agressive bios settings should be made reasonable
ASUS:
DIGI+ VRM Load-line Calibration to Medium
DIGI+ VRM Phase Control to Medium
DIGI+ VRM Duty Control to T. Probe
DIGI+ VRM Frequency to VRM Frequency Mode, 350 Khz <--- I believe this makes the difference.
Extra controller enabled and drivered, but nothing inserted. Disable in dev man.
The sleep issues seem to have been finally solved with latest bios (after 10 months)
There will always be troubles with USB devices, since most are not certified and there are many thousands of them
I could go on and on.....
I have over 150 tips I have accumulated since Jan on P67 Z68 and am still gathering. This mobo rollout mandated doing your homework more than any other. Def wrong time for a beginner to jump in.
To sum up, if you are knowledgeable, theres no reason for any prob with these mobo. They are fantastic!
