Apple is well-known for wanting a close spread in hardware requirements with OS X upgrades, having dropped PowerPC like a hot potato when Snow Leopard arrived just three years after the Intel switch. Whether or not you're a fan of that policy, it's certainly carrying forward with Mountain Lion. When the newly-finished OS hits the Mac App Store, it will rule out the very first wave of 64-bit Macs: certain MacBook Pros, Mac Pros and other early systems will be denied a taste of 10.8.
Engadget , Apple sunsets a few 64-bit Macs with Mountain Lion, video drivers likely the culprit, Apple sunsets a few 64-bit Macs with Mountain Lion, video drivers likely the culprit
