Dell XPS 430 and Radeon HD 6770 and 6670

I have two different dell XPS 430 and following is their configuration

• First Dell XPS 430s:

X48 chipset with DDR3 dual channel
Intel Core 2 Quad QX9650 3Ghz,
Total of 8 GB RAM
XFX PRO 550 Watt PSU
Intel 320 series 80GB SATA II SSD
Seagate Barracuda SATA II 160GB
Quite Old PCI 5-port USB 2.0 card
PCIe NIC x1 2-port USB 2.0 card

• in second XPS 430:

All is same except power supply is of 375 Watts
And 500 GB 7200 RPM HDD

Whenever i try to connect my XFX HD-667X-ZAF3 AMD Radeon HD 6670 or ASUS AMD Radeon HD 6770 on either of my computer then my computer fan starts spinning fast and light comes on. I have tried all the alternatives of connecting those graphics cards on my motherboard but this happens every time i connect them on my both motherboards. It hasn’t harm me but my fan spins so loud that you can hear it outside. Those HD 6670 cards have external power connector and i have noted that if remove those connectors then my computer work properly. I have tried other graphic cards and they all work on my system i don’t know why these cards don’t work on my system!

It is clear that your power supply is not enough for running those graphics cards. You can’t use the HD 6670 graphic card on just 375W power supply. I have 425watts of power supply and i can only use Dell AMD Radeon HD4670 properly. Check the requirements for those graphics cards and do not use them on your system as you may lose your power supply by putting more pressure on him. As you have already said you have seen lights in the power supply.

No power supply can’t be the problem here, as maximum power required by AMD Radeon HD 6670 cards will be 75 Watts and both the graphic cards work properly with both of my power supply units but with different motherboards. This is only happening with my model that is Dell XPS 430.