When news of OS X 10.8 hit the internet yesterday, owners of older Macs collectively held their breath while they waited to hear if their machines would work with the new operating system. Well, The Unofficial Apple Weblog has posted an unofficial list of which Macs are supported under the current developer build of Mountain Lion. Here's the list:

So why are older Macs not being supported? Guesses are circulating that Intel's older GMA 950 and GMA X3100 integrated graphics processors might be to blame. However, since Macs with ATI Radeon and Nvidia GeForce solutions currently run Lion but won't run this Mountain Lion build, we think there's more to the story. The late 2006 iMacs (ATI Radeon X1600) and MacBook Pros (Mobility X1600), as well as the original Mac Pros (Nvidia GeForce 7300) are all on the chopping block too — at least for the time being. It bears repeating that this is not an official list from Apple, and that it only covers incompatibilities with the current developer build of OS X 10.8. The list could easily change in the months leading up to the OS release.