Felix, unfortunately http://support.apple.com/kb/TS4015 and the link you posted (http://support.apple.com/kb/HT4241) both state that this doesn't work with our "outdated" 2009 Mac Pros. So basically I paid a pretty penny for a machine that is nearly comparable to the 2010 Mac Pro, and dropped a TON on this new video card, and now I can't even get HDMI audio out of it without buying a completely new machine. This makes me very upset. Anyone else want to join a petition to get this pushed back into the 2009 Mac Pros?
No success with my MacPro 4,1 and the Radeon 5870 upgrade sending audio through its mini display ports to an HDTV via HDMI when running Mountain Lion (AKA Mac OS X 10.8). Put me down as seriously disappointed. This card supports the feature, and I bought it in good faith, believing that it would work equally well in any of the Mac Pros listed by Apple as compatible (that definitely included the Early 2009 models). It doesn't, and Apple's response is not to fix their software issue, but to put a little note deep in their support forums to tell its customers that, in effect, the card wasn't sold/supported in good faith by Apple.
I'm reminded of the Hitchhicker's Guide to the Galaxy, in which Arthur Dent is told by the nice man that showed up with bulldozers outside his house one day that the planning decision for the demolition of his house had been on display in the public records office for six months, and if he couldn't be bothered to take an interest in local affairs, and lodge a formal complaint at the appropriate time, then the whole matter was his fault. To which Dent replied that when he'd heard about the order for the first time the other day, he gone straight 'round to the council offices to find this order. It turned out that the "public display" area that provided this vital information was located in a basement lacking both lights and stairs, and was within a disused lavoratory with a sign on the door saying "beware of the leopard".
Apple plainly demonstrates that same sort interest in informing its customers of important decisions it has taken with regard to the products it so happily sells to those customers. It's strictly a formality; a retro-active attempt at legal *** covering, buried where customers can't find it until it's too late (especially since they are given no indication prior to the sale that there's any issue they should be digging in the unlit basement of Apple's support forums to discover). Who at Apple makes these unilateral "screw 'em" decisisons, and how on earth are they justified ethically or legally? (Also, may I please be allowed to meet this person in a dark alley with a Nerf bludgeon?) One of the reasons I buy Mac Pros (and Power Macs before them, and so on) is because their initial high performance, along with their expandibility, provides more years of useful life than any other model of Macintosh. That's part of why I pay the high price for a Mac Pro, as opposed, say, to an iMac. In return, it is in no way too much to ask for the machine to be fully supported for at least three years, and considerably more. Especially when the support pertains to an Apple product like the Radeon 5870 upgrade.
I could swear Steve said repeatedly that Apple loves its customers. And this issue dates to his era - so where's the love for its Pro users? I'm not feeling it. (And didn't feel it throughout the "Lion" era when they dropped support for their own software RAID. Again, I have to wonder, who the heck makes these "screw 'em" decisions ... and why do they think harming their Pro users is a good idea?)
Since I don't think there's any mechanism by which we can pursuade Apple to make this right, I hope I will be forgiven by the other people in this thread for needing to let off some steam.