I was upgrading an old ASUS mobo with a couple of sticks of DDR2 2gb per stick. After I pulled old 1gb and replaced them the board would not POST and case and CPU fans would not spin. Power light on mobo was on.
Thinking it was the possible the PS I replaced it with a tested new one and got same problem. I then stripped mobo down and used old ram in same slots. Same problem. I thought that maybe the board got cracked when inserting the new ram. It took some force. So I replaced the mobo and CPU with new ones. The problem is still there. The mobo is a new one so I used fresh DDR3 RAM as that is what this board takes.
The interesting part is in the problem. The board gets power but there is no beep codes are fans spinning. If the power supply is left on and you slowly insert the 24 pin power connector the fans will spin briefly. Holding the connector in but not putting it all the way in you can keep the fans going but there is still no POST. I checked the connector all over for loose wires, pins, partially inserted pins, and cleaned connector with electro-clean. Problem still there.
check under the mb for a misisng standoff or a screw that fell under the mb and is shorting the mb out.
Alreaady checked that but did it again as it is a strong possibility. No problems there. That is why I am totally baffled. I did try another thing since writing the comment and that was to pull all power from all devices and fans except 8 pin and 24 pin MB and CPU power. Tried starting without cpu fan, then with fan, and then another CPU fan. Problem is still there.
On first mobo I did the same but on cardboard. This is why I am posting here. I have lots of experience with this stuff and I am baffled. I must be missing something really basic and simple. The type of thing that makes you bang your head on the workbench.
original board RAM was DDR2 at 800 4x1gb. was replacing the 1gb to 2 gb sticks of DDR2 800. pretty straight forward and have done it many times.
Second mother board uses DDR3 so I plugged in 2 sticks of 4gb 1600. basically went to an almost new puter with new RAM, MB, and CPU. Same PS and a nividia 8600gt 256mb video board as this MB has no onboard video. Last time I used this board it was good. I also tried it with a 8600gt 1gb board just to make sure. No drives or other devices on the power supply and pulled out CPU fan from working box to try here as well to eliminate short in fan motor.
and have you checked populating each memory slot and just using one stick of ram? for instance, second gen Core processors require the 1st dimm slot to be populated on my mobo, that's the second slot from the processor.
Does AMD also have a similar requirement?...idk