That would be correct. However, I cannot tell you if such a card from third-party vendors is actually one ATI made for Apple or one that has been flashed so I would make a point of asking. There are flashed cards around on the market. They will work just fine with one minor problem - you will not see the normal gray boot screen.
Wow, painless upgrade ... Fry's Electronics had the Apple HD5770 for $249. Removed my older ATI 3870, install the HD 5770, got a MiniPort to DVI adapter for my 2nd Dell 24" (my primary is Cinema HD 30") and voila. Everything worked ... booted into OSX no problems. Motion 4 is smoother with improved FPS and everything seems to work a little faster.
Booted into my Boot Camp drive (Vista x64) and installed the latest AMD drivers from their website Cat 11.6 along with CAP 2 (application profiles) and works perfectly, both monitors. Colors just seem to look better, very fast, excellent!
Highly recommend this video card upgrade to anyone running old MacPro like my 1,1.
I was worried about noise, but it's VERY quiet and Motion 4 and Cinema 4D R12 doesn't seem to stress it much.
Wow, 5 years on my MacPro and I haven't really needed get a new MacPro yet ... think this video card will buy my another 2 years (who knows, maybe the "pro" version of FCP X will be ready by then).
Nothing to worry about, the 5770 has the ability to output sound but it's disabled for any MacPro up through 4,1.
Here is a quote on it
What we have here is a bunch of well meaning people getting dragged into a non-problem.
The OP doesn't have a specific problem, he has created one.
Any video card that has the capability to output sound has this entry in the "PCI Cards" section of system profiler.
"Hoolock Parent" is the framebuffer for the video part.
If the OP has a specific problem with the card he needs to state it.
But the vast majority of people with 5770s will see this very same info in their system profiler.
I am fairly certain that later machines that have the ability to have audio sent via MDP will see this supported but most Mac Pros (up through 4,1) have this disabled, hence no driver loaded.
I am not going to waste my time posting screenshots from a 5770 in a 1,1 and a 5,1 to illustrate. This guy has wasted PLENTY of everyone else's time.
"Hoolock" is FB from the original Mac OEM 5770. If it were a flashed card, it would likely be "Vervet" instead.
Here in America, we call this a "Wild Goose Chase"
Nothing to see here folks, move on.