The information was first published by our friends from Barefeats, and is finally official thanks to a TechNote released on Apple website.
The new graphic cards released with the new Mac Pro models are NOT backward compatible with the previous Mac Pro, despite the fact that PCI Express 2.0 IS backward compatible with its previous version. The problem would be linked to the Mac Pro firmware (new one being EFI64, while the previous one was EFI32).
Apple should not in the future forget that most users or owners of a Mac Pro usually invest in such high-end desktop while thinking to be able to upgrade the graphic card, as this is most likely the easiest component to be changed and one of the most quickly outdated. Some users, even decided to go for a Mac Pro instead of a an iMac for having the choice to change the GPU
Maybe, the only way will be to f
