64 bit kernel or not?

Discussion in 'macOS' started by Macmel, Sep 8, 2009.

  1. Macmel macrumors 6502

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    Feb 7, 2008
    #1
    So after reading a hundred million (maybe two or three less) messages on this topic, only confusion remains in my head. So here is a simple question for Mac experts:

    I have an Early 2008 MBP (penryn, model MBP 4.1) which I think is capable of rebooting in 64 bit kernel mode. I have 4 Gb RAM memory and a 2.4 GHz C2D processor.

    WOULD I SEE ANY DIFFERENCE AT ALL IN MY COMPUTER BETWEEN 32-BIT AND 64-BIT KERNEL?

    It's easy, I guess. Thanks for answering in advance.
     
  2. gr8tfly macrumors 603

    gr8tfly

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    #2
    No.

    And if you use K64, you could end up losing capability if you need a 64-bit version of a kext and they're not available (for instance, Parallels Desktop).
     
  3. Macmel thread starter macrumors 6502

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    Feb 7, 2008
    #3
    OK, thanks for the info. I won't bother then with pressing 6+4.:)
     
  4. gr8tfly macrumors 603

    gr8tfly

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    #4
    It won't hurt anything - just keep in mind the possible conflicts. To be honest, I might try it myself to satisfy the engineer in me. :) I wouldn't be able to stay in that mode, though, as I do have Parallels and some USB serial adapter drivers that would get clobbered.
     
  5. Macmel thread starter macrumors 6502

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    #5
    I know it won't be dangerous, but if I'm not going to see any improvement, but probably the opposite... I might try just to see if there's actual conflict.
    I guess I would never benefit from 64bit mode as my computer only supports 4Gb officially (although 6 Gb can be installed and work. 8 Gb make the computer unusable, but don't remember the exact reasons for that).
     
  6. santos79 macrumors regular

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    Feb 25, 2009
    #6
    It remains to be seen whether 8GB will work in 64-Bit mode. The tests that have been done (by OWC) were with Leopard and in 32-Bit kernel mode. Will have to wait until 4GB modules come down in price, I guess.
     
  7. Winni macrumors 68030

    Winni

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    Oct 15, 2008
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    Germany.
    #7
    Snow Leopard is just another "transitional" operating system release. Apple cannot default to 64-Bit yet, because they would break compatibility with almost every piece of software on the market. However, Snow Leopard clearly points into the direction where Apple is going: 64-Bit Intel ONLY.

    My bet is that the next release of OS X will require a 64-Bit hardware architecture to run, but of course it will still have the ability to execute 32-Bit applications. However, the OS itself won't be able to run on 32-Bit Macs anymore. It's just a logical next step, especially since there have not been that many 32-Bit Intel Macs in Apple's product portfolio.

    Anyway. We're still in 2009, and right now it's the safer bet to use Snow Leopard's 32-Bit kernel. ;)
     
  8. maflynn Moderator

    maflynn

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    #8
    No,

    if you had more then 4gig of ram, then you'd be able to use it in SL with the 64bit kernel. As it stands now, you can still run 64bit apps, just that the kernel will boot up in 32bit mode.
     
  9. gnasher729 macrumors P6

    gnasher729

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    Nov 25, 2005
    #9
    The amount of RAM doesn't matter. If a machine can run with a 64bit kernel, it can do that with one GB of RAM just fine. The question is whether it is useful. Apparently MacOS X needs 16 Megabyte of memory in the kernel for every Gigabyte of RAM. No problem if you have 4 GB. If you have 32 GB, that's half a GB of kernel memory which is not nice if the kernel can only have 4 GB for everything. If you have 256 GB, its 4 GB of kernel memory. It cannot possibly work with a 32 bit kernel. So Apple has to go to 64 bit kernel eventually, but it is not needed now.

    I think file system caches are also in kernel memory. A 32 bit kernel couldn't cache more than one or two GB of file system data in RAM. If you had 64 GB of RAM, using say 8 GB for file system cache could be helpful, but it wouldn't work with a 32 bit kernel. Again, with 4 GB RAM it is no problem.
     
  10. maflynn Moderator

    maflynn

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    #10
    My point was that the 64bit kernel provides benefits of accessing greater amounts of ram then the 32bit kernel. Given the fact that OP doesn't have > 4gig mitigates one of them main benefits of the 64bit kernel.
     
  11. SnowLeopard2008 macrumors 604

    SnowLeopard2008

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    #11
    This was THE hot topic to discuss before SL was actually released in the wild. 32-bit kernel will still allow you to execute 64-bit apps, but with software "hacks" or "mods" to allow 64-bit kernel benefits like addressing more than 3GB of memory, etc.
     
  12. maflynn Moderator

    maflynn

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    #12
    You realize that even in Leopard you could execute 64bit cocoa apps right? While it was a hot topic and continues to be one, the fact remains that 64bit apps can and do execute regardless of which kernel boots up. I don't deny that there are hacks and work arounds for apps to try to access more ram but in general 64bit applications don't require a 64bit kernel.
     
  13. netdog macrumors 603

    netdog

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    London
    #13
    How about for configs other than 4GB?

    I'd like to throw another config into the mix.

    2008 Mac Pro 8-Core 2.8 with 8 GB of RAM. When might going into 64-bit mode be useful and when am I better off with 32-bit-mode?

    I both use the machine sometimes for the usual daily stuff, i.e. Safari, Mail, iTunes, VMWare XP, MSN Messenger, Pages, MS Office, Preview, Skype etc. (usually all at once).

    I also use this as my media workstation, primarily using FCE 4, CS3, Aperture and Logic Express.

    On a side note, I have an MBA that is my primary machine for writing and Internet stuff and a little iPhoto when I am travelling. I tend to use all of the apps listed in the first group, quite often with many of them open at once. Obviously this machine has 2GB or RAM. It is a 1.86.
     
  14. maflynn Moderator

    maflynn

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    #14
    the other advantage to using the 64bit kernel is a more efficient instruction set and access to 64bit registers that should cause your apps to run faster. Real world experiences so far have not shown that the current crop of apps benefit greatly to using the 64bit app so to answer your question you'll probably not see many reasons to boot into K64
     
  15. Amigaman macrumors regular

    Amigaman

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    Sep 29, 2007
    Location:
    Greenville, MI
    #15
    I've been using the 64-bit kernel since Snow Leopard came out and the only app that gave me a problem was VMWare Fusion. Thankfully that will be resolved soon. I could switch back to 32-bit until then, but why should I when everything else is running just fine? ;)
     
  16. macrem macrumors 65816

    macrem

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    Mar 11, 2008
    #16
    This is mainly why I boot into the 64-bit kernel by default, also I don't use any incompatible apps (there was one app I had to recompile with 64-bit architecture).
     

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