I didn't flash it so I don't get the boot screen, but I don't really miss it. Reading from the box in my hand, it has the oh-so-catchy-and-memorable name: Radeon R9 280X DirectCU II TOP Have you flashed it, and if so, which precise model did you get? I'm considering this card for my old Mac Pro. You will want to delete the following (prevailing notion is that they're buggy) files to get best performance: I power it combining the little 6-pin PCI power connectors and a molex adapter from the optical bay.
It's pretty much the same thing as the D700 offered with the current Mac Pro but with less VRAM. I can testify that the Asus R9 280X 3GB works great in mine.
