osx, 32 bits, 64 bits, oh my!

Discussion in 'macOS' started by situbu42, May 21, 2013.

  1. situbu42 macrumors newbie

    May 21, 2013

    i looked around for answers all over so please forgive me if these questions have been answered before.

    Given that I have a mac xserve with efi32 and osx 10.6.8. of course it runs with a 32 bit kernel. the machine has a 64 bit processor and will run 64 bit apps.

    1. Can a 32bit app address more than 4gb of memory?
    2. Can a 64bit app address more than 4gb of memory?
    3. If I had efi64 in the machine and booted the 64 bit kernel,
      • Can you run 32 bit apps?
      • Are 32 bit apps a bad idea (based on what you know/experienced)?
      • could a 32 bit app address more than 4gb of memory?

    Do any of the answers above change with 10.7 or 10.8?

    also on the mac in question, in about this mac, software, some apps listed say intel 64 bit = yes. for those that do not, could they detect the 32 it kernel and run as 32 bit but run as 64 bits when there is a 64 bit kernel?

    any links to back up the answers are appreciated (i have to show this to someone else).

    thanks in advance.
  2. maflynn, May 21, 2013
    Last edited: May 21, 2013

    maflynn Moderator


    Staff Member

    May 3, 2009


    Yes you should

    No, just limited to 32 bit address space. Some of my best friends are 32 bits :p

    No, see my first answer. Since the memory structures within the app are 32 bit it is limited to only 4gb of ram.

    I don't believe so, 32bit apps AFAIK still work on Lion

    I'm not sure, I'd hazard a guess some will and perhaps some won't.
  3. Bear macrumors G3

    Jul 23, 2002
    Sol III - Terra
    In short:
    1. No
    2. Yes
    3. -->
      • Yes
      • No
      • No

    No changes with 10.7 and 10.8 I also doubt this will change with 10.9.

    If it does not say "Yes" in the 64-Bit column, they are 32 bit only applications and can not run as 64 bit. It would require an update to the application that has 64 code included.
  4. talmy macrumors 601


    Oct 26, 2009
    No. 2^32 = 4G so that's all it can address.
    No. 64 bit apps are potentially faster because the architecture is better, but 32 bit apps run just fine.

    No, except they don't support a 32 bit kernel.

    The code is completely different, however the binary file can contain multiple executables, such as both 32-bit and 64-bit intel.

    Check anandtech.com -- they've run many articles in the past on the 64-bit OS X. versus 32-bit.
  5. situbu42 thread starter macrumors newbie

    May 21, 2013
    thanks all.

    the machine in question is has MAMP and in about this mac, software, it is listed as intel 64 bit = yes.

    does this mean that the mysql executable is a 64 bit process? how can i check the 64bitness of an individual process?

    thanks again for the fast response.


    famous last words of a 32 bit app hater. :)
  6. situbu42 thread starter macrumors newbie

    May 21, 2013
    never mind my last question. the file command does the job.

Share This Page