PC won't boot with two PCI Express power plugged in

Hey everyone

I have an i5 3570k with a GA-Z77-D3H motherboard using the F10 bios that came with it

I just purchased a new graphics card to upgrade my system. This is the Powercolor Radeon 7870 Tahiti LE.

I previously used a Sapphire Radeon 6670 GDDR5 which did not require any external power connections.

It's not a driver problem because my PC won't even boot when I plug in both the PCI-E connectors. If I just have the card in without plugging in the connects, the system boots but the card isn't detected at all (I assume its not on due to no power).

My PSU is the Antec Earthwatts 650W Green, it has 38amps on +12v so I assumed it would be more than enough. I tried only plugging in power to cpu, mobo, hd, and gpu and it still doesn't boot. The light will turn on but there will be no display and my keyboard doesn't work (I can tell if it works or not because the LEDs light up).

I tried resetting my BIOS to factory settings, then plugging in the card again but it still doesn't work.

I believe the problem is either with the GPU itself (which I just got today)/ the PSU / the PCI-E connectors.

Does anyone have any recommendations?
9 answers Last reply
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  1. The green series is a base model PSU. Even though Antec usually markets good PSU's, sometimes they inflate the stats a bit from the manufacturer, in this case, Delta. For example, my Antec 620HCG is actually a 600 watt Seasonic.


    You didn't say whether it would boot with one plugged in or not? The card will probably have a red LED and will not function as advertised, but it might boot.

    It sounds like your PSU is shutting down due to too much amperage being pulled. The green series is not a premium line and may be getting over amped.

    When you first turn on any device, there is a surge of amperage that is not indicative of its normal draw. One of many reasons I usually buy a PSU that is 150Watts more than I calculate I need. Headroom is important.

    EDIT: I just looked up your PSU specs. If the card will boot with only one SLI connector, get a dual Molex to PCI six pin adapter and use that for the second input. It should shunt half the draw to the other rail. Might work, might not. Otherwise consider replacing the PSU.
  2. Hello Groundrat,

    The PC does boot with one plugged in, the GPU still doesn't work though (not enough power I guess).

    Where is the red LED located to indicate it isn't working?

    My green is 650w and I assumed the 7870 tahiti would require much less, but it seems what you are saying is a huge possibility.

    Let me note, when I have both the PCI-e plugged in, my computer lights up, fans spin, cpu cooler spins, the gpu fan spins too. However, I cannot get anything to display at all. If I don't plug them in or only plug in one, everything spins and the integrated hd4000 works, but the 7870 doesn't.

    Thanks, I will test with another setup in the evening on my cousin's computer running a 4870 and 500w PSU.

    If it is my earthwatts green, do you have any recommendations?
  3. Well I tried the molex and it didn't work. I tried a bunch of variations too. I can't test it on another rig until next week though, any other recommendations
  4. Can you test the card on another system? If it doesn’t come up on that one either, its RMA time. I hope you are still in the RMA window for your GPU.

    Some graphics cards have LED indicators on the bezel to indicate power levels (XFX 9800GTX comes to mind),

    Sorry it didn’t work, it was a long shot. I’d get a Seasonic, or a brand that is made by Seasonic (Antec HCG, Corsair) http://www.tomshardware.com/reviews/power-supply-oem-manufacturer,2913.html
  5. I believe I have 30 days from purchase (from the store) and I've had it for about 2 days now. I can test on another system next friday or so.

    If it is my PSU...
    I was looking into getting the Corsair HX650 or HX750. I noticed the 650 is produced by seasonic but I'm a little iffy because its the same wattage as my earthwatts (and it has only 2 pcie cables incase I ever want to crossfire). 750 is produced by another manufacturer but has 4 pcie cables. The 650 is about 30$ cheaper than the 750, but I'm very wary of cheaping out on PSU now

    Thanks again for the help, I'll report back as soon as I can test it
  6. I did a few more tests today.

    I reset the CMOS of my MOBO by taking out the battery, still didn't work, same symptoms.

    I tried putting it into the other PCI (x4 I believe) slot, the computer turned itself off after a few seconds (Same situation as the other PCI slot, except it actually turns itself off)

    I tried plugging in both PCI-E PSU Power slots without plugging the GPU into the pci slot, this let the computer fully boot up normally (but then obviously no GPU).

    A couple of times I reseated it back into the pci3.0 slot, the computer turned itself off just like the PCIx4 slot after I put it in there, then it went back to how it was before. (Where it turns on but doesn't boot, but without the auto turn off)

    I just found this post: http://forums.tweaktown.com/gigabyte/49687-z77-d3h-pci-express-problem.html

    Maybe it is a mobo problem? Well I will find out if the GPU works when I test it in other systems first, then if it does I would have to figure out if its the mobo or psu...
  7. Sounds like you have a valid testing senario. Check back when you need help.
  8. It's working atm after I updated the bios! Just need to run some tests on the card itself and make sure its stable
  9. groundrat said:
    The green series is a base model PSU. Even though Antec usually markets good PSU's, sometimes they inflate the stats a bit from the manufacturer, in this case, Delta. For example, my Antec 620HCG is actually a 600 watt Seasonic.

    A HD7970 and an OC'd i5-3570k would only use ~300W, nowhere near 650W and the 650W Green is a pretty solid unit that can easily handle over 600W under normal conditions. So unless the OP's PSU was defective, it would be good enough for dual 7970s - this would only bring system power near the 500W mark.
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