New mobo, perma reboot

kopekope

Distinguished
Feb 10, 2011
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18,510
Hello,
I just installed a Phenom X6 1090T on MA770 UD3 with ddr2. And system does reboot every 10 seconds. my PSU is coolermaster 700W. It did reboot without showing anything on the screen when I inserted 8 pin atx but I`ve read on some forum I can insert a 4 pin (the one I used with previous motherboard). So I did it, and... well, now it does reboot and displays me the mobo welcome screen. One time also displayed hardware check screen for few seconds. It said I have ddr2 (but without kb checksum) and UNKNOWN CPU... and it said it was updating bios EC and to not reboot... but it shut down by itself.
What shall I do? What`s wrong?