OS X, on the other hand, has made a more gradual transition between 32-bit and 64-bit, with support added slowly over the course of multiple releases.
Because of this, and because Windows applications and drivers usually have distinct 32-bit and 64-bit versions, Windows’ transition to 64-bit has been slightly rockier and slightly more visible to the user. This is done mostly to maintain Windows’ compatibility with older applications – moving or renaming things like the System32 folder would break programs that expected it to be there – and as a result the two are separated to the point that there isn’t even an upgrade path between 32-bit Windows and 64-bit Windows.
OS X’s 64-bit implementation differs significantly from that of Windows, which treats its 32-bit and 64-bit versions as two distinct operating systems stored on different install media. Now for a history lesson, combined with about as much information about Lion’s 64-bit support as you could ever want. Remember that these processor upgrades, while technically possible, were never supported by Apple. The Lion installer isn’t actually doing checks for processor capability, but for your Mac’s model identifier, meaning that Core Solo and Core Duo Mac Minis and iMacs that were later upgraded to Core 2 Duo processors will still fail to install Lion without modification because the installer assumes they’ll be running 32-bit processors (though if you can get Lion running, your processor should be able to run everything just fine).
Even if it can’t boot the 64-bit kernel of Lion or support 64-bit EFI, any Mac that came with a Core 2 Duo (or any 64-bit capable Intel processor) can install and run Lion without modification.Ĭore 2 Duo-equipped Macs that don’t support OS X’s 64-bit kernel or 64-bit EFI can still run 64-bit apps, which can address more than 4GB of RAM. If you’re not interested in that, though, let me lay out the most important stuff in brief:Ĭore Solo and Core Duo-equipped Macs are the only Intel Macs being dropped by Lion. I’ve seen quite a bit of confusion on this topic (and there was quite a bit when Snow Leopard trumpeted full 64-bit support at its release), so I want to go into some detail about the history of 64-bit OS X. Just as Snow Leopard pulled support for PowerPC Macs to emphasize Intel development, Lion will pull support for x86 to push 64-bit development. Apple usually doesn’t do this lightly – in most cases, dropping support for older models is done to move the platform forward (though, as when 10.4 dropped support for Macs without FireWire, it can also be done to push particular proprietary technology).