Issue was starting 10 days ago. Having up a real stable system for about 2 years.
Not having any hardware problems. Nothing tuned, standard default config.
GA Z97 D3H rev 1.0
CPU i5 - 4460
RAM 16G by having 2 ram sticks 8G installed
10 days ago bootlooping / no postboot, screen remains black. -> check hardware. removed one of the rams -> booting successful !. Tried second time to boot -> bootlooping.
Reinstalled the second ram back (having again both in), system booting successful. After shutting down of windows and starting again to boot -> bootlooping.
Checked CMOS battery -> 3,15 V O.K.
cleared the CMOS -> no success, bootlooping
removed again 1 of the ram sticks. -> system booting.
upgraded from version F6 to BIOS ver. F9. fine, system boots. put second ram stick back, system boots and
works for about 10 days.
Yesterday same story. bootlooping.
Replaced the memory completely by a new ones (again 2 x 8Gb ). system not booting.
reinstalled now BIOS F8. fine, everthing is back, no boot problems.
put both "old memories (ram) back" everythings fine.
Any idea. It seems that the mainboard looses CMOS data.
(A not working dual bios.. ?) No idea.