New graphics card and new power supply: after installing pc turning on and off

I bought a new graphics card gigabyte radeon hd 6570 2gb ddr3. I had 275w power supply back then. After installing the graphics card pc turned on then off.
I asked someone and he said you need 450 w power supply. I then bought a 450w power supply. The power supply ran on previous graphic card (ati x600 series) but giving same problem with new graphics card. Specs:
Optiplex Gx620 Dell motherboard
4gb ddr2 ram
Intel Pentium D 945 3.4ghz
PSU 450w
What could be causing the problem? Is it psu or gpu? Please answer
6 answers Last reply
More about graphics card power supply installing turning
  1. Do you mean it goes right off after you turned it on? That sounds like a short circuit to me, try to only plug in the motherboard + graphics card and test it again.
  2. mhedas said:
    Do you mean it goes right off after you turned it on? That sounds like a short circuit to me, try to only plug in the motherboard + graphics card and test it again.


    When i turned on the switch after installing gpu and psu then pc automatically turned on then half a second turned off and repeated this process automatically without booting anything.
  3. its no working. psu running on previous gpu b ut not this gpu. why ?
  4. did you finally solve your problem? I got the same problem. (similar dell, cpu + hd5450)
  5. Are you sure you don't mess with anything on your motherboard?
    Like swapping power switch with reset switch on the mobo...
    Try start your PC WITHOUT memory (RAM). Get back to us soon. :)
  6. i solved the problems. first i install windows xp, update bios to A11, change video setting in bios (from auto to onboard/PEG), shut down, put in graphic card and switch pc on.
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