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Computer will not boot with 8pin CPU power connected plugged in


I hate to ask for help, but I have gotten a bit desperate finally. I own a dell xps 9000. I had recently bought a GTX 470 and a Corsair 650Watt modular power supply to upgrade my system. However, after plugging everything in, the system would not boot. I noticed that if I did not connect the 8 pin power plug to the cpu power on the motherboard, the entire system would start (drives spin, fans start, etc) but not even load the BIOS screen. The power light stays on (amber) which means there is some power related problem.

However, when I put my old stuff back in (the PSU and video card), the problem did not go away.

Does anyone have any experience with this matter? Did I somehow fry the motherboard (or worse, the cpu)? I really hope it isn't something that bad...
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  1. First, make sure ALL the hardware is properly seated in their respective slots.
    If still no go, try some breadboarding.
  2. Best answer
    And it won't boot without it. :)

    Work through our standard checklist and troubleshooting thread:
    I mean work through, not just read over it. We spent a lot of time on this. It should find most of the problems.

    If not, continue.

    I have tested the following beeps patterns on Gigabyte, eVGA, and ECS motherboards. Other BIOS' may be different.

    Breadboard - that will help isolate any kind of case problem you might have.

    Breadboard with just motherboard, CPU & HSF, case speaker, and PSU. You do have a case speaker installed, right? If not, you really, really need one. If your case or motherboard didn't come with a system speaker, you can buy one here:

    You can turn on the PC by momentarily shorting the two pins that the case power switch goes to. You should hear a series of long, single beeps indicating memory problems. Silence indicates a problem with (in most likely order) the PSU, motherboard, or CPU.

    Motherboard LED's mean very little. When on, all they are telling you is that the computer os plugged into a live power socket and the PSU is switched.

    Remember, at this time, you do not have a graphics card installed so the load on your PSU will be reduced.

    If no beeps:
    At this point, you can sort of check the PSU. Try to borrow a known good PSU of around 550 - 600 watts. That will power just about any system with a single GPU. If you cannot do that, use a DMM to measure the voltages. Measure between the colored wires and either chassis ground or the black wires. Yellow wires should be 12 volts. Red wires: +5 volts, orange wires: +3.3 volts, blue wire : -12 volts, violet wire: 5 volts always on. Tolerances are +/- 5% except for the -12 volts which is +/- 10%.

    The gray wire is really important. It should go from 0 to +5 volts when you turn the PSU on with the case switch. CPU needs this signal to boot.

    You can turn on the PSU by completely disconnecting the PSU and using a paperclip or jumper wire to short the green wire to one of the neighboring black wires.

    This checks the PSU under no load conditions, so it is not completely reliable. But if it can not pass this, it is dead. Then repeat the checks with the PSU plugged into the computer to put a load on the PSU.

    If the system beeps:
    If it looks like the PSU is good, install a memory stick. Boot. Beep pattern should change to one long and several short beeps indicating a missing graphics card. Silence or long single beeps indicate a problem with the memory.

    Insert the video card and connect any necessary PCIe power connectors. Boot. At this point, the system should POST successfully (a single short beep). Notice that you do not need keyboard, mouse, monitor, or drives to successfully POST.

    Now start connecting the rest of the devices starting with the monitor, then keyboard and mouse, then the rest of the devices, testing after each step. It's possible that you can pass the POST with a defective video card. The POST routines can only check the video interface. It cannot check the internal parts of the video card.
  3. Hey, thanks for the reply. I had read through that after I found it when browsing after I made my post. I do not have a case speaker, so I ordered one and will see what happens then. I've tried just about everything else on that list already except taking the whole thing out (really wanted to avoid that part, eh, didn't think it could be a seating of the motherboard issue since I never moved that at all), I'll do that next after I get home later today.

    It's been so long since I have had to mess with a computer (Pentium 4) since I went to laptops as I moved around for quite some time. Not sure if I have any thermal paste on hand, so I am a bit hesitant to take a look at the seating of the CPU fan. I really hope it is some sort of simple issue.
  4. Best answer selected by Alexsiev.
  5. Well, the motherboard is burnt. Ah well, crap happens.
  6. This topic has been closed by Mousemonkey
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