First boot, CPU seems to get no power, please help!

[yiplong]

I am putting my computer together and I have a problem here.
I am booting the build in a cardboard box, on the mobo I have CPU & HSF, RAM, video card. When I turn the power on, the video card fan spins, but not the CPU fan. I then connected the CPU fan to a different power source on the mobo, and it worked, so the fan is not the problem.
I turned on the monitor, the gigabyte logo screen is displayed and then it goes into some other thing that I don't recognize. The build does not post.

Since the CPU fan is working, but won't spin when connected to the CPU_Fan power source, it appears that the CPU is not getting any power. (I touched the area right around the chip, and it doesn't appear warm.

The CPU is powered by the 2x4 12v ATX power connector right? To that I connected two 2x2 wires, marked "CPU1" and "CPU2". I tried plugging them in different ways and found that they only go in one way.

Can someone please help me troubleshoot this?

MOBO: Gigabyte MA770T-UD3P
CPU: X3 720
PSU: OCZ StealthXstream 770W

[Ulti]

You have tried reseating your CPU right? I assume you have reconnected the power connectors, also give the 24 pin one a little wiggle though to make sure that's in tightly too.

Have you tried booting with 1 stick of RAM also?

Other than that, could be a faulty CPU/motherboard/PSU or RAM without knowing more details.

[yiplong]

Thanks for your reply. I tried it again and was able to get into BIOS. CPU voltage and frequent were listed, so my prior assessment must have to be wrong. The CPU does get power. To confirm this, I connected a case fan to the CPU_Fan connector on the mobo, and the fan worked.
So based on the above testing so far, we can draw these conclusions:

- CPU has power is working properly, my prior assessment was wrong
- my CPU fan (Xigmatek S1283) is working, it does not spin when connected to CPU_Fan connector, but works when connected to another source
- The CPU_Fan connector on the mobo is working as well, b/c it can power a case fan

So why when I connect the S1283 to the CPU_Fan connector, it doesn't spin? This is so weird. I couldn't have connected it wrong, because it has a fool-proof design that only inserts one way.

[Ulti]

So now the PC boots up fine?

I've not had any Gigabyte boards but I'm assuming that your CPU is running really cool and there are perhaps fan profiles which may rule that the fan won't start up until the CPU reaches a certain temperature.

On my DFI board the fan profile is set on default to not start the fan up until the CPU is over 25 degrees C so when I have a 4pin (PWM) CPU fan, it won't spin up at all until the CPU temp gets above 25 degrees. However, I've replaced my CPU fan with a 3 pin fan and the motherboard can't control it via PWM and can only lower the voltage to 5V usually so whatever 3 pin fan you connect will spin.

Hope that's what's happening, if not then I'm not sure but I'm pretty sure this is the case. Fan profiles are usually under the hardware monitor menus in case you can't find it.

[yiplong]

so to test whether this is the issue, I can change the fan setting in BIOS to force the fan to be always one, and it should come on?
I should try this. Thanks so much.

[Ulti]

Yup, there should be an option to turn fan profiles off or you could raise the temperature too.

Looking at the manual, it mentions CPU Smart Fan on Pg53:
http://europe.giga-byte.com/FileList...70t-ud3p_e.pdf

[yiplong]

I did exactly that and the fan starts right up. Everything is working perfect, installing windows now. I will reenable the feature when everything is set up and ready to transfer the board to the case.

Thank you so much.

[Ulti]

Glad to know everything is working fine, have fun with your new build!