ATI Radeon HD 5870 not working! HELP!

[Zeninox]

I have installed my new ATI radeon on my mac pro 1,1 2006, and when i turn the mac on it comes a black screen and then a white screen for a second, and black again! I have tested the card on one of my friend's pc's, and it worked perfect! put on my mac it doesn't work. I have also two 6-pin power connectors that works fine. can anyone help me? Sorry for my horrible english , here is my specs

Prossecor: 2 x 2,66 GHz Dual-Core Intel Xeon

Ram: 4 GB 667 MHz DDR2 FB-DIMM

System software: OS X 10.8.4

 

[MacVidCards]

Why not take a moment and tell us about the important part, the 5870?

Which model and what connectors and how are you connecting to display?

 

[Zeninox]

Im using two 6 pin pci-e mac pro connectors, I use a DVI to HDMI (HDMI on the screen) and here is the card http://www.amd.com/en-us/products/graphics/desktop/5000/5870

 

[666sheep]

VGA to HDMI? Do you mean DVI to HDMI? Why don't you just use HDMI cable?

 

[bax2003]

Im using two 6 pin pci-e mac pro connectors, I use a VGA to HDMI (HDMI on the screen) and here is the card http://www.amd.com/en-us/products/graphics/desktop/5000/5870

I would like to see that VGA to HDMI cable.

 

[Zeninox]

I would like to see that VGA to HDMI cable.

Srry i ment DVI to HDMI

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VGA to HDMI? Do you mean DVI to HDMI? Why don't you just use HDMI cable?

Yes i mean DVI to HDMI
I have tried. didn't work