Thanks for the information, cmn699. I just bought a PSU tester for around $15 dollar at amazon, and I will get it on the 12. Hopefully it is not my mobo failure.
After I clear CMOS (remove battery and put it back, I wait for around 60 seconds to put the battery back), my computer then was only on 2 seconds (with normal beep sound, nothing on the screen), and the computer restarted by itself,(with normal beep sound again. this time the screen is on with gigabyte logo) and stay at the mobo splash screen. In this situation, do you consider the my PSU is fail?
If the problem of boot failure was due to CMOS corruption [ from repeated changes in hardware /reboots etc during numerous troubleshoots with shut down /restarts , Forced shut down , Power interruptions ] or incorrect CMOS entries by the user if you clear CMOS by cutting of Power from the CMOS coin battery to CMOS chip , on reboot BIOS should automatically prompt you with a message " Upload Optimized default BIOS and boot or Reboot " which will change the CMOS entries to the way it was when you bought the MoBo. You will then be 'allowed' to enter BIOS set up and reset the date from many previous years (when original BIOS was set ) to current and re-input all the required options for the intended OS to boot.
If at this stage the MoBo manufacturer's Splash screen just hangs there blocking you from entering the BIOS setup with Hotkey (Del in GA) you have to consider some serious hardware problem might have occurred.
At this stage strip the hardware one after the other from MoBO connectors starting from HDD which is one of the most common causes of this problem and leaving Video and RAM for further booting.
If you don't have another PSU and you got to wait a few days to test the PSU, then just shut down the Computer, pull PWR cable off from PSU socket, , remove the coin battery and leave that Computer overnight like that and reconnect all next day and see if it will boot and let you change BIOS setup.
Even if that happens , I will still consider Power Supply Unit as the problem hardware and rule that out as the other things like MoBO and CPU are more expensive and you don't want them to be the ones in trouble.
This is one of the worst enigmatic computer problems in my experience. You are not going to get much literature about the causes and troubleshoot as very few report the problem in a systematic way.
I have faced it and was happy to change a Brand new Corsair CX650M I had in that System with a new Thermaltake Tough Power Grand Series RGB 750 W PSU at the very last minute before I considered to remove the CPU Cooler/CPU and remove the MOBO and send MoBO RMA to Amazon. That Corsair CX650M passed the Test on tester!
Just to prove the diagnosis was right, I reinstalled the Corsair and the Splash screen Freeze returned and was reversed by the other PSU.
I was happy in that there was very little down time and cost of fixing the problem a lot better than otherwise.
Some of the so-called Smart PSUs we see these days if malfunction can confuse us really bad.
If you have any doubt about your Clear CMOS procedure( I don't think so based on what you have posted) repeat removing the CMOS battery for longer time before re-inserting and rebooting..
I suggest shut down PC. Press On/OFF switch a few times to discharge the Capacitors. Then remove CMOS battery. Wait 5-6 minutes and reinsert. Just to make sure you have not failed that step.
