A collection of computer systems and programming tips that you may find useful.
Brought to you by Craic Computing LLC, a bioinformatics consulting company.

Tuesday, June 19, 2007

'Modern' ATX Motherboards have TWO Power Connectors

I just put together a new machine with a ASUS P5B Deluxe motherboard, Core 2 Duo CPU and a load of other good stuff. I built a similar system with the same motherboard a few months back and had no problems at all on the hardware end. I must have actually read the manual that time.

With this system I put everything together, double checked it and powered it on. The fans worked, the red and blue LEDs on the motherboard lit up as expected but there was no video output and no beep from the system... dead to the world.

After changing the video card, unplugging the drives, and swapping out the memory I was still getting nothing. The fact the there was not even a beep code from the motherboard had me thinking it was a bad board or a bad CPU. I needed a break so I took the dog for a walk...

Refreshed, I took another look at the system, checked the cables and... oh... OK...

Modern ATX form factor boards like this Asus P5B have TWO power connectors - the 'regular' 24 pin EATXPWR that has been around for a while, plus a 2x4 pin EATX12V connector.

If, like me, you forget about that one then the system will not boot... says so right there in the manual... in small print, on page 33...

On my board the socket for this is on the 'top left' corner by the keyboard, etc. sockets. You can use either a 4 pin plug or an 8 pin plug of the correct type. The board comes with a small plastic cover over 4 of the socket holes, so you need to remove this if you want to use the 8 pin plug.

So, a simple mistake to make... but one that took me well over an hour to figure out, dang it.

1 comment:

Steve McGahey said...

I'm so very glad you make this little complaint public! Just went through the same issue with a new Intel motherboard. I had the impression that the power configurations were either a 20 pin plus a 4 pin, OR, a 24 pin by itself (with no need to an extra 4-pin... as if the 4 pin was the difference between the 20 and the 24).

So, I had the same issue, and had been wondering if I should risk frying my new PC. By 1:30 AM, I no longer cared, and split an 8-pin cable and stuck it in. Miracle of miracles... I got me a POST beep. Such a sweet, sweet sound.

Now, if I could just get the onboard DVI / HDMI to output...

- Steve.

Archive of Tips