New Macbook Air with 64bit kernel?

Discussion in 'MacBook Air' started by Mechinyun, Nov 4, 2010.

  1. Mechinyun macrumors 6502

    Jun 24, 2010
    Anyone switched theirs on? I saw its still 32 by default.
  2. inf macrumors 6502


    Nov 22, 2006
    Helsinki, Finland
    What do you mean still 32bit default? Snow Leopard is always running with 32bit kernel by default. Why would Apple change this and get lot of complaints from users whose programs don't work anymore.

    Lion will probaply be fully 64bit by default.
  3. henry72 macrumors 65816


    Jun 18, 2009
    New Zealand
    Especially when Mac doesn't need 64-bit to support 4GB of RAMs :D
  4. animan macrumors member

    May 1, 2010
    With 32 bits one can address upto 4Gigabytes (2^32 = 4294967296).
    Did you mean more than 4GB?
  5. Scottsdale macrumors 601


    Sep 19, 2008
    I think this is a bogus part about Apple marketing their Macs as 64-bit. If they don't run a 64-bit kernel, it's not truly 64-bit OS anyways.

    However, I have read that it can run a 64-bit kernel, and it can also run 64-bit Windows in Boot Camp now too. Are those two statements fact or fiction???
  6. maflynn Moderator


    Staff Member

    May 3, 2009
    Actually on newer MacPros, OSX boots up with the 64bit kernel by default.

    In OSX and Linux flavors that use a PAE enabled kernel, you can access more then 4gb of ram, even though the kernel is 32bits.

    The need to actually run a 64bit kernel is largely mitigated because of this, and the small performance improvements that it offers is largely offset by the overhead needed to manage the 64bit kernel and larger data structures, at least it is on slower computers with 4gb or less ram.
  7. Fuchal macrumors 68020

    Sep 30, 2003
    They can run a 64-bit kernel, but it's disabled by default for much improved driver compatibility. It runs 64-bit Windows fine.

    Inside the 32-bit kernel, you can run 64-bit applications, and many of them are 64-bit, so I don't see what the problem is.
  8. gustav531 macrumors member

    Oct 22, 2010
    I have very little knowledge about this 32, and 64 bit things.
    But, what if there is two versions available for a program, 32 and 64 bit. What version shall I install on my new snow leopard 2010 MBA?
  9. bcaslis macrumors 68020

    Mar 11, 2008
    Snow Leopard is a full 64 bit OS. The kernel itself and run either 32 or 64 bit, this has no effect on other applications (or on Windows 7) running 64 bit. The kernel running in 32 bit is actually a benefit in many cases. One of the problems Vista encountered was that a 64 bit kernel means all extensions (drivers for printers, etc...) must be 64 bit to work. This caused a lot of compatibility problems. Running just the kernel in 32 bit allows older drivers to work. Additionally the kernel itself with todays machines never needs to run 64 bit since it never needs to access more than 4GB for the kernel tasks. In theory there is a tiny percentage performance improvement in running it in 64 bit mode.

    To force the kernel into 64 bit there are a few methods. One is to hold "6" and "4" while booting. However this is a thread on the Apple forums that this doesn't work on the new MBA air. I've tried a few things myself and can't get it to work. Nobody outside Apple seems to know why this is. But the MBA hardware identifies itself as 64 bit capable so it should be possible somehow.

    Short summary is that you are running a 64 bit OS. It's just the kernel running in 32 bit mode for compatibility and this does not affect anything else.

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