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Bad Power Suppy?

I just built a new pc and it wont turn on! I have;

AMD Phenom II 940 Quad Core 3.0GHz
Gigabyte GA-MA790GP-UD4H MOBO
G.Skill 1066 DDR2 Memory 2X2GB
PSU Rosewill DR-8500BTX 500W.

I installed everything, I have no Hard drive hooked up to it yet, I turn it on the fans start going but seem a little slow. The board has onboard graphics so I am plugged in via RGB nothing fancy. Monitor neverer does anything ever! It will not load to the BIOS or I cant see it maybe? I took the heatsink and fan off the CPU and turned it on the CPU is not getting hot at all its not doing anything and the system doesn't shut off, it should since i took the heatsink and fan out and unplugged it right?

Does this sound like a PSU, Motherboard, or Processor issue. Everything is brand new and I just dont know what to return first?

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8/22/2022 - Mon

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OK so i am looking at the 4 prong 12v connector on the PSU but i dont see just a 4 prong port on the MOBO, i see a 8 prong. Should I just take the 4 prong and plug it into half of the 8 prong on the MOBO. I did try unplugging the memory and the main atx power connector. The fans seem to run slow and the the Processor doesn't even do anything it just stays cold and the clock doesn't make any noise.

Thanks for the help Steve.

Oh Steve its working. You are the man bro. I plugged in the 4 pin and its going.

The 4 pin and 8 pin you speak of are for CPU power.
They use more pins to handle more amps to keep from melting wires or burning pins.

Your processor is 125 watts.
Assuming your VRM is 80% efficient (which on the good side) the power to the motherboard for CPU power is bit over 156 watts.
At 12 volts that's 13 amps.
With a 4 pin connector (which only has two +12v paths) that is 6.5 amps per wire and per pin.
Not sure about the wire (depends on size) but those pins are only rated for 5 amps each.

You need to get an adapter so you are spreading the CPU power over more pins.

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