This may solve all of ur problems!!
Ok this is long so I apologize in advance but this may help alot of people who are thinking that thier motherboard is bad when it may not be. Ok so a couple weeks ago i decided to make a leap fromm ddr2 to ddr3. i ordered an awesome Asus board which had sata 6 gbs, USB3.0, and AMD 890gx chipset. i go the board in the mail I put it all together and fired up the board more excited than a 12 year old on christmas day that just opened up an xbox 360. lol. Well to my dismay it never posted that day. Everything would turn on even the HDD motor but no video and no post. The dram has a checklight that lights up during the posting sequence that is supposed to light up everytime but it was only doing it sometimes. if it lights up then turns off that means your ram is ok and it will boot. If it stays on that means the ram is not listed in the manual on the QVL and that it needs adjustment before the sytem will post. Well it also has a neat little function called Memok which automaticaly sets the ram to a safe speed and voltage so the board can boot it. I used this function and all of the sudden the system posted. It said to enter Bios and save the ram settings and all will be fine. Well the problem was that the board seemed like it would only check if the ram is there sometimes and most of the time the Dram check light would never light up. Which seemed to me 1 of 3 things. The Bios needed to be updated. The memory is completely either dead or non compatibe. Or the motherboard is messed up and is not always checking to see if the ram is there. So I went to the shop and picked up a stick of memory that was in the QVL list in the manual. I put it in and it immediately started doing the same thing that my other RAM was doing. So i used the MemOk option and let the board boot into windows. It was really unstable and slow. i went to the Asus website and updated to the latest Bios. that didnt work either. So i figured the board was bad and filled out a newegg return RMA form. I was frustrated to go with no pc for a week or two but I wasnt going to sit there and have to keep my case open and have to use the memok option every time I wanted on the computer and plus with updates and downloads and stuff of that nature the pc has to be restarted and since it would not restart most of the time I figured I was screwed I had to return the board. plus I spent $150.00 on a board that i want to OC my memory andall that good stuff. I unplugged my pc from my basement and brought it upstairs gettin ready to take it all apart. For some reason or another I didnt want to believe I had to return the board because the thought pissed me off quite a bit. In a last ditch effort I plugged in the pc with a different cord from another pc and all the sudden it booted. it booted b4 though when I got lucky so I figured that was just a lucky try. I turned it off and hit the power button again. BAM!! the mofo posted again. And again and again. It pure amazement i was like WTF?? the problem was I had a faulty new plug that came with my psu. the wire that connects from the wall to the psu. I have never thought of that because I have never seen one of those fail before unless it caught on fire or something. I am sooo happy now no RMA's 4 me. the reason I wrote this is to let anyone who has tried everything to get their new board to post this just might b your problem. I had my last board plugged in to this and that one booted but I could never get as good OC on my graphics card at all on that board I believe this to also be the fault of that same cord. Even if this post saves a person just 1 board I will be happy. good day all and good luck my friends!!