You won't be able to run applications (primarily games, I guess) using the Metal API. At the moment there are exactly 0 of them, so it's no big issue.
Upcoming OS X games might use it, but you have to consider that we're talking about a 2006 MacPro, high-end AAA titles would be a problem either way.
Yeah, hopefully I could steer clear of Metal-based programs. One can still use the OS just fine on their older card. In fact (and as an update to the list from Apple that I gave you), Apple claims that any Mac that can currently run Yosemite will be able to upgrade to El Capitan. Now, we know that the 1,1 and 2,1 Mac Pros technically shouldn't have El Capitan on them (Or Yosemite, Mavericks, or Mountain Lion, for that matter); however, if the graphics chip in a 2007 iMac is fine enough for El Capitan, then my Radeon 5770 should be good. This other list was compiled in an article. I don't know if this list is specifically for El Capitan, or if the article simple stated that any Yosemite-compatible Mac would be able to run El Capitan, and simply stuck in the requirements for Yosemite...
- iMac (Mid-2007 or newer)
- MacBook Air (Late 2008 or newer)
- MacBook (Late 2008 Aluminum, or Early 2009 or newer)
- Mac mini (Early 2009 or newer)
- MacBook Pro (Mid/Late 2007 or newer)
- Mac Pro (Early 2008 or newer)
- Xserve (Early 2009)
I guess it's legit. Here is an excerpt from a Wikipedia article about El Capitan; let's all hope and pray that we don't necessarily need to worry about Metal for some time.
All Macintosh products capable of running OS X Yosemite are supported by El Capitan, which includes all models supported by OS X Mavericks and most models supported by its predecessor
OS X Mountain Lion.
[18] However, not all features are available for each model. Apple notes that Metal is available on "all Macs since 2012".
[19] It is speculated that the
GPU must at least support
OpenGL 4.3.
[20]
The following models are compatible with OS X El Capitan:
[21]