GTX-470 with less power than it calls for?

I have an HP z400 workstation that comes with 475W of power and -- believe it or not -- the power supply is "custom" and can't be replaced with an ATX power supply that's larger! (At least, not unless I can "maybe' get away with making a home-made adapter to rewire the power cabling to the system board:

I bought an nVidia GTX-470 and am anxious to utilize the CUDA-enabled capabilities that Adobe Premiere Pro CS5 takes pretty remarkable advantage of.

However, the GPU says it should have a "minimum of 550W of power."

As I said, the z400 only has 475W and it apparently can't be increased (at least not without the "possible" mod mentioned above, which I don't even know if I can do or not -- a Corsair forum admin -- who spells out he is not a Corsair employee -- said NOT to do it unless HP will "guarantee" me the system is fully compliant with the ATX 2.01+ standard, which their techs are totally unable to find any information about).

So, now I have to ask: What happens if I try to use the GPU with the power supply that came with the machine? Will it "maybe" work okay? Is it a question of "It will either work fine or not at all, and you can only find out by trying?"

Or, is it "very risky" in that I could seem to be working fine but then unexpectedly experience data corruption? (Which of course could also mean OS corruption and thus a massive amount of time re-installing everything.)

Note that I want to put a total of five SATA 7200 drive into the machine, too, run by an LSI 8888ELP controller card.

Also note that I did a partial test so far. I tried to boot the machine with the GPU installed and it did go into a boot screen successfully. I haven't taken it past that yet since there is no OS even installed on the machine yet (and I don't want to risk problems right off the bat.)

Note that with the existing 465W power supply I do have connectors for the two PCI-Express power connectors that have to go onto the GPU. (One is achieved with a PCI-Express connector coming out of the power supply, and one is achieved with an adapter that came with the GPU that converts two molex plugs to one PCI-Express connector, which I hope is okay.)


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  1. With only 475W HP PSU, i'm afraid you'll push it to it's limit.
    Can you give us more detail about it's amperage? amperage on 12V rail(s)?
  2. wa1 said:
    With only 475W HP PSU, i'm afraid you'll push it to it's limit.
    Can you give us more detail about it's amperage? amperage on 12V rail(s)?
    What does it mean if I do push it to it's limit. That doesn't sound like simply suffering a performance degradation. It sounds bad. :(

    Amperage on which, the PSU or the GPU?

  3. By the way, someone suggested I look for an after-market power supply that works in the HP z400 and provides the additional wattage. I've already searched the web quite a bit and nothing comes up. Should I keep looking? Any idea where?

    Thanks again!

  4. Here's a link to the label on the power supply that came in the z400 machine:
  5. With that PSU, it's "very risky" to run GTX 470 with it...
    This is a difficult situation, since your case is not accept any other ATX PSU...
    Just a little advice, next time, build your own PC. :)
  6. I am definitely a convert as of the past 24 hours, and your advice further cements that. I already had a tech configure a PC for me from components on NewEgg. For as soon as I can afford it. Hopefully soon.

    For now, though, a very interesting potential solution has come up.

    I happen to have this extra PSU here, a Corsair HX750W, which is modular.

    What happens if I leave the original PSU in the machine, and separately I leave the HX750W "outside" of the machine and run two PCI-Express power cables from it to the GPU?

    A hardware guru on the Adobe forum who actually works for Adobe just suggested that I try that. He makes no guarantees but sees no reason it shouldn’t work and no reason it should pose any issues at all.

    Other than logistics, it seems realistic to me, too, and I don't see any issues either.

    Just cables to wrestle with when I want to move the machine, that's all, which is easy with this modular PSU.

    What I'll probably want most is "extension cables" for the two PCI-Express cables, that's all. If I can find those, I'm probably a happy camper, right? (Until I can afford to build the new machine we listed the parts for, which I really look forward to.)

    What do you think?
  7. Yes, it should work, 1 PSU for your system and 1 special PSU just for GPU, yes it should work, your PC might looked awful but it doesn't matter, as long as your system is running, right... :)
  8. Well, my solution is actually leaving the second power supply outside the machine, on the floor behind it. That's right where the video card is anyway, at the "bottom" of the machine when it's standing on end in normal use, and I can slip two 12" "extension" PCI-Express power cables through an empty PCI slot (I'll know for sure when they arrive from NewEgg tomorrow. That will leave me a few inches of cable out the back of the machine to plug into. Should be just fine.

    And Corsair's website, when beginning to create a support ticket for a power supply, shows in an FAQ for testing the power supply, which two pin positions on the 24-pin system-board plug to jump "with a paper clip" to keep the power on. Seems simple.

    Thanks again!
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