SnowLeopard and 64-bit.

It looks like not all users understand  about 64-bit support in snow leopard.

So, here is how it works:

on all Macs, except xserve, system boots by default 32-bit kernel.

This kernel can run 64-bit apps justs fine on core 2/core i7 based cpuz.

64-bit kernel works only on macs with 64-bit efi, this is limitation set by Apple,

technicaly 64-bit kernel can be launched by 32-bit efi just fine.

also Apple disabled 64-bit kernel support for any macbooks, even  with 64-bit efi.

64-bit Kernel can run both 32 and 64 bit apps.

On hackintosh only cpus with ssse3 can run 64-bit kernel/apps, its core2/corei7 based cpus.

if kernel is 64-bit, then it can load only 64-bit kexts.

if kernel is 32-bit, then it can load only 32-bit kexts.

Userspace program cant load plugins with other architecture, for example menumeters will work only when you booted legacy, so menubar created by 32-bit application.

Quicktime uses InterProcess Communications(IPC) to load 32-bit codecs in 64-bit player.

64-bit safari uses IPC to load 32-bit flash player plugin.

To try to boot x86_64 kernel on Macintosh,  edit this file:


find there:

<key>Kernel Flags</key>

and change it to

<key>Kernel Flags</key>


  1. youminbuluo
    August 14th, 2009 | 5:59 pm

    thx for interpretation~~~~~

  2. twr
    August 14th, 2009 | 6:07 pm

    does the 64-bit mach_kernel / 64-bit EFI limitation explain why boot-think or chameleon still lack SL support (a special ‘boot’ file needed by the second as all your readers may knwo …), or am I totally wrong about this (too) ?

  3. August 14th, 2009 | 6:18 pm

    my system boots default in x64 … 10A421 did and 10A432 also … on Asus P5W with 8GB and 8800GT … no Problems … thanks for decrypter :-) and the other stuff !

  4. August 14th, 2009 | 7:52 pm

    i think by default none of the PPC kexts will be made 64 bit so that will be sort-of a indirect way of getting all that legacy bull crap out of there.

    even though the g5 is technically more of a true 64 bit platform then intel.
    no i am not missing the g5, well i may have if they ever made apps and os
    work good with the it.

    its like apple new the g5 was going to be a terd even before they sold it.
    i bet they knew all about plans to go to intel before they released g5 imacs and powermacs for us all to get raped on… garbage.

    Reason for 64 bit for the normal person:
    the ability to have more then 2gb ram…

    what makes a pc or mac or hack truly fast? Enough ram and Fast Mass Storage.

    i don’t think the transition from 32 to 64 bit anything will be noticeable. That is why it has taken so long, x86 abortion that lives on…. yay.

  5. Joshua Ochs
    August 14th, 2009 | 8:07 pm

    “i bet they knew all about plans to go to intel before they released g5 imacs and powermacs”

    Ah, more uninformed ranting from the peanut gallery.

    If you’d care to look at the timeline, this was also when the Pentium 4 was running out of steam in a major way and the Ghz advances there had stopped. Of course, both the G5 and P4 were using INSANE amounts of power and generating enormous amounts of heat – which led to the ill-fated liquid cooled G5’s. IBM promised they could improve the clock speed and efficiency – and dropped the ball. Intel recognized the problems and came knocking with the “Core” roadmap, which dumped the entire P4 NetBurst architecture for a more P3-based design, but with emphasis on efficiency and multi-core instead of raw Ghz. Apple liked what they saw, and said as much when they made the switch – “performance per watt” was much better. That was announced in June 2005.

    And here we are today. But at the start of the G5 era (June 2003), there was NO reason to think that Intel was going to handle it better than IBM.

  6. August 14th, 2009 | 8:23 pm

    Still the x86 Abortion lives on…. enjoy

  7. August 14th, 2009 | 8:44 pm

    ///no personal attack, find another place for it

  8. Nexos
    August 14th, 2009 | 9:33 pm

    i have original macbook alu unibody

    i have set my kernel flag to arch=x86_64
    have nvidia grahic but when i reboot and tipp uname -a in terminal
    it shows me
    10.0.0 Darwine Ker… /RELEASE_I386 i386

    i think that is i386=32 Bit
    have i do something wring?
    i wont 64 bit?

  9. zillion
    August 14th, 2009 | 11:18 pm

    I’m assuming this is just for Snow Leopard

  10. bozz_2006
    August 14th, 2009 | 11:32 pm


  11. Aaron
    August 14th, 2009 | 11:56 pm

    Does this mean that the original Mac Pro won’t be able to boot a 64 bit kernel since it has 32 bit EFI?

  12. netkas
    August 15th, 2009 | 12:05 am

    Aaron, have a macpro1,1 and wanna try ?

  13. bozz_2006
    August 15th, 2009 | 12:17 am

    more than likely, unless apple decides to break character and offer certain updates to a machine that is 2 generations removed from relevancy.

  14. bozz_2006
    August 15th, 2009 | 12:24 am

    netkas, I’ll try it, if you can walk me through it and you can tell me with confidence that i won’t fuck my machine up.

  15. bozz_2006
    August 15th, 2009 | 12:24 am

    also, I am running leopard, do i need to be running a snow leopard build to do this?

  16. UberDuper
    August 15th, 2009 | 3:17 am

    If I come across a copy of the GM seed I’ll give it a whack on my 2006 mac pro this weekend. Seems like another reason to go hackintosh.

  17. Andreas
    August 15th, 2009 | 7:16 am

    i am a bit confused about the kernel flags for 32 / 64 Bit Kernel mode.
    I use -x32 or -x64 with PC EFI 10.2 boot and Chameleon RC2.
    If i use Chameleon RC2 (640) and not overwrite the boot file with EFI 10.2 boot,
    i get an KP very, very early at boot time.

    So in which boot loader versions / mixes SL can boot and with what Kernel flags.
    Or are arch= ony synonyms (means boot loaders know both -xnn and arch= )

  18. ovof
    August 15th, 2009 | 8:37 am

    Can’t make RADEON HD3870 work in sl :( :( :(

  19. zillion
    August 15th, 2009 | 9:26 am

    Guys, It’s really simple actually

    Leopard = 32 bit Kext(s)

    “Snow” Leopard = 32 and 64 bit Kext(s)

    Would seem it should work on 10.5.8 but no they don’t.

    “I know your asking then why do I have 8GB RAM and I’m still i386 sorta speak ?”

    Well, I’m assuming only that the Darwin Kernel was modified for this “Long” ago.

    Anyway, The only thing to do to get a true 64 Bit system is install “Snow Leopard”

  20. walterav
    August 15th, 2009 | 9:27 am

    VMware Fusion 2.05, doesn’t work with SL in 64 bit, my system is running in 64 bit by default I think? Is it because VMware Fusion is using 32 bit kernel modules?

    uname -a shows “x86 x64″ instead of the “i386″ other people talk about…

    I used chameleon rc2,+dsmos+openhaltrestart+dsdt.aml, and replaced “boot” file with a “boot” file with this
    don’t know where it came from … but it works great!

  21. Bonyo
    August 15th, 2009 | 1:12 pm

    How can I determine if my EFI is 32 or 64 bit? Thanks.

    ///type this in
    ///ioreg -l -p IODeviceTree | grep firmware-abi

  22. zod
    August 15th, 2009 | 1:42 pm

    Can’t my RadeonHD 3850 to work, can only boot in safemode right now….

  23. sip
    August 15th, 2009 | 8:31 pm

    I did this:

    Kernel Flags

    and change it to:

    Kernel Flags

    When I typed uname -a in terminal, I got this

    Darwin MacPro2008.local 10.0.0 Darwin Kernel Version 10.0.0: Fri Jul 31 22:46:25 PDT 2009; root:xnu-1456.1.25~1/RELEASE_X86_64 x86_64

  24. SY
    August 15th, 2009 | 9:05 pm

    Okay, I have a 2.4 Santa Rosa MBP. I checked the EFI and it said:
    “firmware-abi” =
    I am Running: Mac OS X 10.6 (10A432)
    I changed my /Library/Preferences/SystemConfiguration/

    Kernel Flags

    Yet I still get: 64-bit Kernel and Extensions: No

    What am I doing wrong? I know its just the Kernel but I am dying to try it out. Is my computer not supported?

  25. The Rominator
    August 16th, 2009 | 1:22 am

    Tried the trick on 1st Gen Mac Pro

    Still a “NO” in the 64bit line is System Profiler

    ////the only way to boot x64 kernel on ur macpro is to use hackintosh bootloader(pcefiv10.1) installed to usb stick

  26. August 16th, 2009 | 1:30 pm

    […] helped me: SnowLeopard and 64-bit. __________________ Support MacTalk by shopping at the Apple Online store via this link! My […]

  27. grib
    August 16th, 2009 | 5:36 pm

    do a verbose boot and read 3rd line, says if 64 bits enabled/

  28. Jingu
    August 16th, 2009 | 8:12 pm

    I’m booting Snow Leopard build 10A432 in 64-bit mode without even trying.

    I’m on an old NAPA platform laptop (32-bit chipset), and I’m booting from a USB stick with Chameleon 2 RC1 and the PC EFI v10.1 boot file.

    Without even using the arch=x86_x64, SL boots by default in 64-bit mode.

    And I get in System Profiler: 64-bit kernel and extensions: Yes

    The problem is that all my kexts have to be 64-bit or they won’t load. I have qe/ci with silent natit 64-bit, but I still don’t have any sound or internet.

  29. Jingu
    August 16th, 2009 | 8:22 pm

    On my previous post, I forgot to mention that I have a Core 2 Duo T7200 processor (64-bit processor) and a ICH7-M chipset (32 bit). Still, SL boots by default in 64-bit mode.

    The one time I tried to boot in 32 bit mode with arch=i386, it gave me a kernel panic.

    /////-x32 boot key to force 32-bit mode

  30. August 16th, 2009 | 8:53 pm

    […] # 64bit & 10.6 # […]

  31. David
    August 17th, 2009 | 12:24 pm

    Hello. I install SL on my MacBook2,1, but i cannot boot in 64bits mode. It is possible install PC_efi on real mac for boot en 64bits mode?
    How can i create USB for try it?

    Thanks a lot

    ///get usb stick, partition it as mbr drive with 1 hfs partition, in disk utility
    ///install chameleon2 rc2 to this disk, uncheck any extra kexts in install configuration
    ///replace “boot” file in root of this disk ( its hidden by default), with boot file from pcefi v10.1
    ///boot from this stick.

  32. August 17th, 2009 | 1:11 pm

    Macbook Pro 3.1 MA897:
    worknout:~ crazyASD$ ioreg -l -p IODeviceTree | grep firmware-abi
    | | “firmware-abi” =

    ///macs sux

    ///$ ioreg -l -p IODeviceTree | grep firmware-abi
    /// | | “firmware-abi” = < "EFI64">

  33. managed
    August 17th, 2009 | 1:40 pm

    How can I see if I am running on 64 bit?
    On System Profiler I see that 99% of kexts have Yes checked at 64 Bit

  34. August 17th, 2009 | 6:09 pm

    I can try in Mac Pro 3.1, iMac 24 (mb418), iMac 20 (mb417), Mac Mini (mb463), Macbook Pro 15 (mb470), Macbook Alu (mb466), Macbook White (mc240), Macbook Pro 17 (mb766), Macbook Air (mb003) and Mac Pro rev.A

    ///so try

  35. August 17th, 2009 | 7:22 pm

    When i finished with all these models i will post the results here.

  36. August 17th, 2009 | 7:47 pm

    All the machines listed in my post are EFI64 except Mac Pro rev.A.

  37. August 17th, 2009 | 7:55 pm

    What a hell? Who changed my post?

  38. August 17th, 2009 | 9:31 pm

    I’m trying to do this:
    ///get usb stick, partition it as mbr drive with 1 hfs partition, in disk utility
    ///install chameleon2 rc2 to this disk, uncheck any extra kexts in install configuration
    ///replace ?boot? file in root of this disk ( its hidden by default), with boot file from pcefi v10.1
    ///boot from this stick.

    But I can’t install chameleon2 rc2 in my usb stick, i get this:

    ///you need to partition it with diskutlity as mbr disk with 1 macosx partition.

  39. David
    August 17th, 2009 | 11:17 pm

    I follow all your instructions for create chameleon2 rc2 boot USB. i have replaced boot file, but when i push “Option” key for boot, only appear my harddrive and not USB.
    WHat is the problem?

  40. LcTrKiD
    August 17th, 2009 | 11:21 pm

    I have the same problem like David now

  41. August 18th, 2009 | 12:57 am

    I still cant install chameleon in the usb stick. I tried mbr, guid …

  42. LcTrKiD
    August 18th, 2009 | 2:03 am

    My problem was i have been trying to install chameleon in Snow Leopard. Now i can install in mbr partition and guid partion but i can’t boot from the usb stick. I press “option” and only appear my hd …

  43. August 18th, 2009 | 12:38 pm

    I can do the 64 bit trick in all efi64 machines i have here but I can’t do that in my Mac Pro Rev.A

    ///what exatly machines u tried ? , name and model, like macbook3,1, etc

  44. August 18th, 2009 | 1:58 pm

    I did the following, install rEFIt in my usbstick in partition 1 and chameleon rc2 + boot from pc efi v10.1 in partition 2. Now I can choose the Snow Leopard from legacy boot but I get “boot1 error”

  45. LcTrKiD
    August 18th, 2009 | 3:46 pm

    Mac Pro 3.1, iMac 24 (mb418), iMac 20 (mb417), Mac Mini (mb463), Macbook Pro 15 (mb470), Macbook Alu (mb466), Macbook White (mc240), Macbook Pro 17 (mb766), Macbook Air (mb003) and Mac Pro rev.A

  46. August 18th, 2009 | 4:08 pm

    mb418 and mb417: imac9,1
    mb463: macmini3,1
    mb470: macbookpro5,1
    mb466: macbook5,1
    mc240: macbook5,2
    mb766: macbookpro4,1
    mb003: macbookair1,1

  47. netkas
    August 18th, 2009 | 4:47 pm

    and which of them were able to boot x64 kernel?

  48. August 18th, 2009 | 5:20 pm

    All! The only one not is my Mac Pro Rev. A . Can you help me with the usb stick boot ?

  49. August 18th, 2009 | 5:55 pm

    I’m sorry!!! macmini3,1 and all macbook (macbookair1,1-macbook5,1 and macbook5,2) can run x64 kernel :(

  50. August 18th, 2009 | 6:08 pm

    I mean CAN NOT run x64 kernel :S

  51. August 18th, 2009 | 7:30 pm

    This might be a silly question, but can’t Apple just update the EFI to 64bit in machines that currently use a 32bit EFI? Or is that not possible?

  52. August 18th, 2009 | 7:33 pm

    Additionally – can Apple remove the artificial limitation that 32bit EFI can’t boot 64bit kernels?

  53. August 18th, 2009 | 10:07 pm

    At the top of thread, lord_webi stated his Asus P5W runs in 64-bit mode (by default no less!). This is a 975X chipset board.

    I would be very happy if this were actually true because I have four 975X boards myself, but have a hard time believing it. Can anyone else verify that 975X, or any other hackinstosh chipset for that matter, in fact stably runs Snow Leopard in full 64-bit mode?

  54. laserbeak
    August 18th, 2009 | 11:27 pm

    Hi, I installed Chameleon 2 rc2 on USB stick, replaced boot with pcefi v10.1. It didn’t show up as bootable so I used the “bless” command on the boot file and directory and now it shows up as bootable when I press option during boot and I select that as a startup and it seems to be loading from the USB stick, then just boots whatever volume I had selected in the Startup Disk preferences. Is this the way it’s supposed to work, or am I supposed to see a new menu or something if booting from the USB stick? I still can’t seem to get SL booted in 64 bit kernel mode even using 6+4 and putting it into kernel options in the boot plist. I have a first-gen MacPro1,1

    Am I doing something wrong? Please help. Thanks!

  55. Acc97_turbo
    August 19th, 2009 | 4:04 am

    Thanks, it’s works for me with MBP 2.53 Ghz mid june 2009.

  56. SL_Cat
    August 19th, 2009 | 6:54 am

    OK, I have a MacPro 1,1. It does run some apps in 64bit (shown in Activity Monitor), but the Kernel is 32. I tried to install Chameleon2 RC2 on my 16GB USB Stick formatted with 1 OSX partition (Extended, not journaled) and as MBR (not GUID!). I got the install error, and that’s it, so I cannot test the procedure on that particular system.

    Any ideas about what I am doing wrong here?

  57. Mo
    August 19th, 2009 | 8:08 am

    “64-bit Kernel can run both 32 and 64 bit apps.”

    It should probably be noted that this also applies to the 32-bit kernel, too (in everything from 10.5 onwards).

  58. August 19th, 2009 | 10:51 am

    […] supuesto, aunque tengas un firmware que no está en la lista, puedes arrancar SL en 64bit con el bootloader de Netkas. […]

  59. António
    August 19th, 2009 | 11:07 am

    I have a MacBookPro3,1 with 10A432.

    The command “ioreg -l -p IODeviceTree | grep firmware-abi” returns “EFI64″;
    I have added “arch=x86_64″ to the file and booted in verbose mode. Near the beginning of the boot messages I see the text “64-bit mode enabled”.

    However, System Profiler still reports “64-bit Kernel and Extensions: No”…

  60. August 19th, 2009 | 12:49 pm

    @SL_Cat Try to install chameleon in Leopard not Snow Leopard.

  61. August 19th, 2009 | 4:44 pm

    […] Via | Netkas […]

  62. MCmonkey
    August 19th, 2009 | 7:43 pm

    I am wondering , have new mac mini 2009
    changed boot.list (copy to desktop changed string arch and override orginal)
    but still i do not boot into 54_kernel why?

    because i have 32bit soft installed?

    ///probably you cant because apple disabled such abilities for minis

  63. laserbeak
    August 19th, 2009 | 10:31 pm

    Has anyone gotten a MacPro1,1 to boot with the 64-bit kernel?

  64. Ed
    August 20th, 2009 | 3:20 am

    What about iMac7,1?

    Doing “ioreg -l -p IODeviceTree | grep firmware-abi” reports “firmware-abi” =

  65. MrAndros
    August 20th, 2009 | 8:54 am

    Im stuck at preferences. Cant find that System map or any apple boot thing

  66. brzeczypudlo
    August 20th, 2009 | 11:54 am

    Have the same problem as laserback here on my MacBook2,1. Formatted the usb stick as MBR / osx journaled, installed Chameleon 2 RC2, replaced the boot file with the one in the PC EFI 10.1 release. Had to “bless” it in order to be able to boot from it. Still “64-bit Kernel and Extensions: No”. Any help would be appreciated. Thanks.

  67. managed
    August 20th, 2009 | 3:56 pm

    Netkas, can you explain what’s the advantage of running the 64 bit kernel. I’ve made the changes on my macbook and everything works slower.
    Applications run slower and the os boots slower.

  68. SL_Cat
    August 20th, 2009 | 8:20 pm


    That makes sense. Now I just have to find me a system with Leopard 😉 I’ll try and let you know.

  69. August 21st, 2009 | 2:58 am

    […] vem da turma adepta ao “Hackintosh“, usando o PCEFI, conforme pode ser conferido no forum oficial dos […]

  70. MacUser
    August 21st, 2009 | 6:50 pm

    Hi all,

    I’m a bit confused. If you set a MacBook to boot in 64bit mode then what happens. Will it start normally in 32bit mode? Or won’t it start at all?

    ////it will start 32-bit

  71. MacUser
    August 21st, 2009 | 7:09 pm

    And another question: the The Intel Core Duo processor is a 32-bit processor. Can it run a 64-bit Snow Leopard?


  72. MacUser
    August 21st, 2009 | 11:41 pm

    And another question: the The Intel Core Duo processor is a 32-bit processor. Can it run a 64-bit Snow Leopard?


    I read up some more. The no means “no 64bit Snow Leopard kernel”, right. I read in an article “64bit applications will run just fine (including benefits) on a 32bit kernel in Mac OS X. Since this was already possible in Leopard, I assumed people were well aware of that. ”

    So if my limited understanding is right then the 64bit Finder of Snow Leopard will run on a 32bit Kernel. Or am I now completely lost?

  73. MacUser
    August 21st, 2009 | 11:42 pm

    Sorry, scratch that. That was dumb. It’s late here.

  74. MacUser
    August 21st, 2009 | 11:48 pm

    My question is: I have a MacBook Pro and a MacBook, both with a C2D and a 32bit EFI. If I change /Library/Preferences/SystemConfiguration/ from
    Kernel Flags

    Kernel Flags
    then will it start the kernel as 64bit or has Apple some other checks somewhere?

  75. Paul
    August 22nd, 2009 | 12:26 pm

    Hello all,

    I have a little question. Can we will use Grand Central Dispatch and OpenCL with a GTX260 ? Because it seems that for OpenCL, only few Nvidia (and few ATI) are listed as compatible (from official site):

    NVIDIA Geforce 8600M GT, GeForce 8800 GT, GeForce 8800 GTS, Geforce 9400M, GeForce 9600M GT, GeForce GT 120, GeForce GT 130.
    ATI Radeon 4850, Radeon 4870

    ///GDC is for cpu, not gpu
    ///opencl works on all nvidia dx10 cards
    Thanks. 😉

  76. Paul
    August 23rd, 2009 | 11:22 am

    Ah, I thought that GDC dispatchs to all CPU core AND GPU core available. Too bad.
    So for use the power of graphical cards, only OpenCL. But even it’s facilitate and fast to adapt softwares now, programmers still needs to adapt their soft ? Is it really so difficult to create a system that “forward” CPU access to GPU access (with auto adapting instructions, etc.) when CPU is full used for example, even it’s not threaded applications ? So ALL softwares will use the power of our computers, and programmers will not needs to adapt their softwares… :-/

  77. Andrea De Micheli
    August 23rd, 2009 | 11:24 am

    Hi. I have a 64bit capable EFI (iMac7.1). SL boots in 32bit even adding this kernel flag: arch=x86_64
    Booting with “6” and “4” won’t work either.

    When I uname -a, i get this result:
    [code]xnu-1456.1.25~1/RELEASE_I386 i386[/code]

    Is there more than 1 version of Snow Loeard? Have i installed the 32bit one?!

    64bit apps work great and fast.

  78. madhias
    August 23rd, 2009 | 7:50 pm

    when booting “-v -x32″ 3rd line says 64bit, kernel i386. boots fine.

    when booting “-x32 -v” or just “-x32″ i can’t boot and there’s no 3rd line about 64bit.

    do i have a wrong syntax?

  79. shadowmajk
    August 24th, 2009 | 1:46 pm

    Its OK, but i think apple will rewrite all components of system to 64bit and relase it in Updates :)

    I w8ing for 64bit iTunes ;/

  80. August 24th, 2009 | 10:27 pm

    […] 很好解釋了為什麼我的熊貓機(MacBook)不能跑 #SnowLeopard 的64位模式… //重點不是在CPU,是在EFI上(這個是蘋果的限制) […]

  81. MCmonkey
    August 25th, 2009 | 12:05 pm

    So really Guys, No one out there who can tell me how to run
    my core duo 2 P8400 in mid 2009 macmini 3,1 to run this 64 bit kernel

    There is now a tool called : 32- or 64-bit Kernel Startup Mode

    It says 64bit cpu 64 bit efi and 64bit kernel but it lies… (about my mac>sys-profiler)

    I changed the boot string and i press 6+4 nothing…

    I wish to test quarzcomposer in 64 bit…

    ///i guess it just changes boot.plsit or addes arch=x86_64 property to nvram

    Anyone a suggestion for me…

  82. Demat
    August 26th, 2009 | 1:00 pm

    I have a MacBook with C2D and 4GB RAM and I installed the GM version of Snow Leopard and and I followed the instruction about to fix for 64 bit but it is unsuccessful.

    Though it is showing 64 Bit Enabled on the Verbose mode but it is not showing ON under the System Profile.

    Anyway idea what is wrong? Need some help.

    Thanks :)

    ///list of supported machines for 64-bit kernel was posted already by many mac sites

  83. August 26th, 2009 | 5:29 pm

    […] Netkas hat aufgezeigt, wie man diese 6 und 4 Blödheit übergehen kann. Um diese Restriktion mit dem dauerhaften Tastendrücken auszuschalten, sollte man also folgendermaßen vorgehen: […]

  84. August 27th, 2009 | 8:19 am

    […] Snow Leopard GM not booting into 64-bit mode automatically, fix here | 9 to 5 Mac SnowLeopard and 64-bit. […]

  85. sebastien
    August 27th, 2009 | 9:23 am

    I am a owner of a macmini coreduo.
    I have upgraded the cpu to a core2duo some times ago…
    If I understood, I have a macmini effi 32 bits with a 64 bit cpu now. In my case, I do not think that apple will give an effi 64 bits update a day because the computer is supposed to have a 32bits cpu…
    I could also run a 64 bit kernel with the pceffi on usb,
    is it right ???
    Is there a real benefit on this machine ???
    Is there downside to boot a mac on pceffi ???

  86. August 27th, 2009 | 4:13 pm

    I have P5WDH Deluxe (I think ICH7/975X chipset) running Snow Leopard 10a432 with the Chameleon RC1 10.1 auto-installer bootloader and it seems to be running in full 64-bit quite reliably. In fact, same problem as Lord Webi above my hackintosh kernel panics regularly in 32-Bit but runs quite stable in 64-Bit. Network works perfectly too but no accelerated CI/QE graphics for my ATI Radeon HD3870 or sound working yet though. I’m sure 64-Bit hacked kexts will appear eventually, otherwise will just buy the best suitable NVidia card and a USB sound adapter.

  87. MacUser
    August 27th, 2009 | 7:56 pm

    under 10.6 the System Profiler displays whether the kernel is running in 64-bit mode or not.

    Does any one know how to read that setting via the terminal? Or how the system profiler reads the setting (I’m guessing it is a boolean value)

  88. August 27th, 2009 | 9:31 pm

    […] und “4” gedrückt werden. Im Falle eines MacBook kann es nötig sein einen Eingriff an der vorzunehmen: sudo pico […]

  89. August 28th, 2009 | 11:27 am

    […] changed a setting in /Library/Preferences/SystemConfiguration/ As per here: SnowLeopard and 64-bit. There is an easier way here: Startup Mode […]

  90. marjohn
    August 28th, 2009 | 4:38 pm

    Hi Netkas,

    After a week of installs and re-installs, finally solved my problems of KP’s just after the GUI loaded, and I am now using EFI 10.1 and cham 2 RC1.

    My question is >

    When I boot with just the -v flag, I seen no 64 bit entry as the 3rd line, if I use -x32 then I do so a 64bit line!

    Also, when using

    ioreg -l -p IODeviceTree | grep firmware-abi

    it always reports EFI64, no matter what param I start with.

    Am I missing something?

  91. August 29th, 2009 | 1:29 am

    […] Posted originally on […]

  92. Derrick
    August 29th, 2009 | 4:31 pm

    DO NOT DO THIS! After upgrading to SL everything was fine. Once I tried this it made my MacPro 8 core 16GB Ram system an unpredictable nightmare. DANGER WILL ROBINSON DANGER. The apple support tech was aghast (yes he could have not made me feel so ignert) that anyone would touch the apple plist files. His quote was “Even Level 2 Techs are warned NEVER touch the apple core files.” I reloaded the entire OS and things have returned to normal. SL IS a 64 bit OS. the “kernel” discussion should not be made to imply otherwise.

  93. Garrett
    August 29th, 2009 | 6:56 pm

    For MAC Intel hardware users on this post – Do you really want MACH Kernel to be X64?

    uname -a shows I386, Profiler software shows 64 bit extension = NO, but look at the extension section, they all show 64bit,

    ///waht shown there is arch of files on disk, not arch of loaded into memory kexts

    look at activity monitor, most programs and system demons show 64bit. The EFI even may show 64bit. What is going on?

    Your system is running true 64bit and not thunking in anyway, but if you change the kernel Architecture to X86 vs I386, then only 64bit drivers can be used. It may cause problems with the many 32bit drivers out there for printers (HP, Cannon, Lexmark…) or the VPN software (Cisco, Aventail…), raw camera drivers, 3rd party firewalls….

    X64 is more for servers where no 3rd party drivers are installed. Parallels and VMware do have some issues when the ARCh is changed to ONLY 64.

  94. August 30th, 2009 | 8:54 pm

    […] The only Mac model that boots with a 64-bit kernel by default is the 2008 and 2009 Xserve (Xserve2,1 and Xserve3,1) running Snow Leopard Server. The following Macs can boot in 64-bit mode in non-server Snow Leopard if you hold down the 6 and 4 keys on boot or if you modify your “/Library/Preferences/SystemConfiguration/” file as described at Netkas: […]

  95. August 30th, 2009 | 11:54 pm

    I think Garrett explained it perfectly. So basically 64-bit kernel will remain a hindrance until all 3rd party hardware drivers and plugins (such as VMware, printer drivers, camera drivers, etc.) are recompiled to become compatible. Better to have a truly backwards-compatible 32-bit kernel than a shiny new 64-bit one that does not yet work with all 3rd-party or legacy 32-bit only apps… anyways thats my take on it as my 2008 White 13″ Macbook 5,2 will not load the 64-bit kernel yet… will Apple eventually change this with an automatic update at some point in the distant future when the majority of 3rd party hardware developers have shifted their kexts to 64-bit?

  96. Charles L
    September 1st, 2009 | 4:50 am

    I held the 6/4 keys for reboot and measured performance before and after using Xbench. With the exception of some of the random disk access, everything was slower with the 64-bit kernal. Not much slower, but slower nonetheless. Hard to see why should run in 64-bit mode. FYI: I’m on a “iMac8,1″ with “Intel Core 2 Duo”, 2.8 GHz, 6MB L2 Cache, 2GB ram DDR2-800, 1.07 GHz bus, boot rom version IM81.00C1.B00.

  97. Lars
    September 1st, 2009 | 6:17 am

    Can you install chameleon2 rc2 and use the pcefi on the hard drive without needing the usb key to boot the 64 bit kernel? 2.0GHz MacBook (MB061LL/A), don’t want to have to remember the key all the time.

  98. David
    September 1st, 2009 | 11:14 pm

    My shows this:

    bplist00“VKernel\Kernel Flags[mach_kernel[arch=x86_64

    ///google -“Property list editor”

  99. muckman
    September 2nd, 2009 | 3:49 pm


    wanted to boot into 64bit kernel on MacPRO 2,1 using chamelon + pcefi 10.1 usb stick.
    with rEFIt i get “Error while (re)opening install volume.
    without rEFIt the stick doesn’t seem to do anything – just boots from standard volume.
    I blessed the stick with ‘bless –folder /Volumes/stick –file /Volumes/stick/boot –legacy’

    any idea?


    ///need to boot it via bootcamp

  100. Matthew Shapiro
    September 7th, 2009 | 10:16 pm

    I’ve installed chameleon on my usb stick using 10.5, copied the new boot file, and have refit installed. Refit sees the usb stick but can’t boot from it. No K64, only K32. I’m sure I’m missing something. The 32-64 bit startup mode shows I should be k64 ready (core 2 duo and efi 64), but no k64. It’s a MBP 3.1.

  101. September 17th, 2009 | 12:35 am

    […] Snow Leopard’s 64-bit processing is being over-sold.  Unless you have a MacPro, or a recent-model iMac or MacBook Pro, the chances are that your hardware can’t address all of the extra memory.  In theory, the double word length of a 64-bit operating system should yield some benefits, but only if the applications are also compiled to run in 64-bit mode – and it won’t be a huge performance increase.  Many applications aren’t yet compiled for 64-bit, including the most memory-hungry application that many digital photographers use – Adobe Photoshop (although Lightroom is).  On the other hand, if you’re buying a new Mac, put as much memory in as you can (third party memory is generally less expensive than the memory that Apple will sell you) but, also, be aware that Snow Leopard’s 64-bit mode needs to be activated manually at startup (although a third party startup mode selector is available) and may not even apply to your hardware, even if you have a 64-bit CPU. […]

  102. September 26th, 2009 | 12:21 am

    […] 1) Here is a link on how to make 64-bit a permanent boot mode: […]

  103. Michelasso
    September 28th, 2009 | 4:59 am

    Hi Netkas,
    I have a MacBook 2,1, with EFI 32. I eventually managed to install Cham 2 RC3 with boot 10.1 in a USB Pendrive and have it showing pressing option at the boot time. Still OSX boots in 32 bits. I also use the kernel startup mode selector to chose 64 bits, nothing.

    Now it’s not clear to me anymore. I thought that Chameleon + PCEFI were supposed to substitute the Mac EFI and load straight the mach_kernel file in the desired arch (64 bits by default): What am I doing wrong? Has anyone been able to boot the 64 bits kernel with an EFI 32?

  104. font9a
    October 8th, 2009 | 7:49 am

    It’s probably been mentioned before… but 64-bit kexts won’t give you ANY benefit unless you have TERABYTES of RAM that your *kexts* are using.

    Booting into 64-bit mode kernel has absolutely no performance or stability advantage over 32-bit mode. In fact, you’ll probably see LESS performance because drivers haven’t been all that optimized for 64-bit, and 64-bit just has a lot of overhead for almost everything a driver does.

    Case in point: on my MBP 4,2 2.6Ghz, 6GB RAM, 512M 8600GT, 256GB Corsair SSD 240MB/s Read & 200MB/s Writes, screen redraws and finder operations (icon refreshes) are MUCH faster in 32-bit mode than 64-bit mode. I’ve been testing this since SL was officially released and it’s the darned truth.

    Lightroom 2.5 64-bit is every bit as fast in 32-bit kext mode as in 64-bit, if not faster, since screen redraws are faster. I can easily load every single adobe CS4 master suite app, every microsoft office 2008 app (incl entourage), every mac pro app, every ilife app, etc. and get (nearly save a couple hundred MB for the OS) all 6Gb of RAM committed — so 64-bit does not enable you to use more than 3GB system RAM like Windows does. 32-bit does just fine (even better) (up to 64GB I think?)

  105. font9a
    October 8th, 2009 | 7:55 am

    I might also add that iPhone tethering will not work in 64-bit mode (but will work just fine in 32-bit kext mode, once you have it set up correctly).

  106. October 8th, 2009 | 3:12 pm

    […] explicación la he encontardo en  un post de Samuel Campos, creado originalmente por, muchas de las dudas que se me han planteado estaban ya resueltas en los comentarios, esto me […]

  107. matylda
    October 23rd, 2009 | 6:21 pm

    Hi I have a proble I just can find in Library/Preferences/

    the SystemConfiguration

    all the files.plist are in preferences and also there is no

    so I created one

    but it still boot in 32

  108. October 24th, 2009 | 2:29 pm

    So, what’s the advantage in boooting up as 64 bit? I don’t use Safari and I’m not sure iLife 09 or FCE 4.0 can use 64 bit. AFAIK, I have no other apps that are 64 Bit unless it is something native to 10.6.1. So What’s the deal?

  109. Sherif ElShamy
    October 27th, 2009 | 9:18 pm

    i tried this method to boot in 64bit mode and it worked normally but everytime i restarted or shut down my machine all motherboarf settings reset, do anyone have any idea how to pass this problem

  110. FrenchPhil
    October 28th, 2009 | 4:59 pm

    There is a thread on InsanelyMac about MB settings reset. Known as a Snow Leopard problem with Gigabyte MB.
    The workaround is to patch a DSDT.aml.

  111. konteudos
    November 9th, 2009 | 5:25 pm

    Thanks !!

    I used this to start always in 32bit mode , because in 64bit mode my usb WIFI do not work :( so now I am booting in 32 bits and with wifi support :)

    used arch=i386


  112. December 21st, 2009 | 5:24 pm

    […] were worried about being stuck in the slow lane with a 32-bit EFI quickly discovered the various workarounds for booting the x86_64 kernel on a 32-bit […]

  113. January 2nd, 2010 | 4:45 am

    I Bought a New Mac Pro 2,1 (8 Core 2007) The Mac Pro 2,1, with EFI 32. was not what Apple said it was I needed 100% 64Bit I/Os & Data paths I hate so much is that my machine I was told was 100% 64Bit is NOT! Apple I will not pay you to go from a MacPro 2,1 (first dual-cpu, quad-core MacPro) to a MacPro 4,1 (Nehalem x 2) You lied you need to step up & deal with your LIE I feel I am owed a TRUE 64Bit Mac Pro no hacks no oh thats older YES Apple it is if you did not Lie to me telling me YES 100% 64 BIT, I would NOT have bought it! I feel false advertising is NOT RIGHT YOU OWE ME MY MONEY BACK OR A REPLACEMENT NOW you should be sorry you tricked me & lucky I don’t Join a Class Action suit. I am so MAD!

  114. January 25th, 2010 | 4:01 pm

    The original 13″ Unibody MacBooks (i.e before they were rebadged as “Pro” machines) *will* boot a 64bit kernel, but it requires a little bit of hacking in order to make it happen:

  115. February 15th, 2010 | 1:43 am

    Joshua Ochs: Thank you for debunking.
    I have a blog article on this history:

  116. sam
    March 21st, 2010 | 2:59 pm

    I also had issues with iPhone not syncing properly when booted up in 64-bit.. Might want to hold off on that until Apple release the next update to SL.

  117. Jackobyte
    April 21st, 2010 | 6:23 pm

    Any update on the iPhone sync issues? Also why would the Internet Tethering not work, is it something to do with the Apple Mobile Device driver not being 64-bit compatible? I mean surely on a regular Mac this issue doesn’t exist, does anyone know how we can get this to work, this is the only issue I have :-)

  118. Emmanuel rm
    May 19th, 2010 | 4:28 pm

    Hola, tengo una macbookpro de 13 pulgagas, la ultima en el mercado, y cuando voy a ejecutar el programa -32- or 64-bit Kernel Startup Mode Selector- para que corra en 64bit me aparece como icono una x y signo de corrección, entonces esto indica que mi equipo si puede correr en mac, nose que hacer? lo que se es que no me deja colocarlo a 64bit, porque me da un error código 5000

    que hago¿? esperando que puedan ayudarme, me despido, saludos.

  119. Dukowsky
    August 26th, 2010 | 2:54 am

    In this case what should i do? i don’t understand very well but i was trying to process with this instructions

    Edit this file:

    Change this:

    Kernel Flags

    To this:

    Kernel Flags

    But this is what i found on my file.


    bplist00”YBoot LogoVKernel\Kernel Flags_)\System\Library\CoreServices\BootLogo.png[mach_kernel[arch=x86_64 -Ye

  120. Dukowsky
    August 26th, 2010 | 3:02 am

    i don’t know if this is the correct setting but i want to know before do any change in this file. I have a core 2 duo and EFI64 and (imac11,1) that was the result of “Kernel Startup Mode Selector”

  121. Dukowsky
    August 26th, 2010 | 3:18 am

    Hi all i was trying to process with this instructions

    Edit this file:

    Change this:

    Kernel Flags

    To this:

    Kernel Flags

    But i found this in my “”

    bplist00”YBoot LogoVKernel\Kernel Flags_)\System\Library\CoreServices\BootLogo.png[mach_kernel[arch=x86_64 -Ye

  122. ptesone
    October 18th, 2010 | 9:38 pm

    will -force64 be the same as arch=x86_64 ?

    just curious. . .

    running snow leopard 10.6.4 AMD Phenom Hackintosh on 750a nForce

  123. January 11th, 2011 | 3:55 pm

    […] EFI chipset are prevented from loading the 64-bit kernel, although there are claims that this is an arbitrary decision by Apple rather than a technical concern, with a hack using the Chameleon boot loader devised to […]

  124. wahid
    July 14th, 2011 | 6:30 pm

    hi gyz! i have a sony vaio laptop based on 64 bit system, i wanted to run snow leopard on it through VMWare but it did not run and gave this error “A virtual CPU has entered the shutdown state. This would have caused a physical machine to restart. This can be caused by an incorrect configuration of the virtual machine, a bug in the operating system or a problem in the VMware Workstation software. Press OK to restart the virtual machine or Cancel to power off the virtual machine.”

    can any body help me with this please???

  125. tangles
    September 7th, 2011 | 12:20 pm

    I have a 2006 Xserve. Therefore 32bit EFI.

    How would I go about trying to get this to boot 64bit? rEFIt?


  126. May 25th, 2012 | 12:31 pm

    This was an amazing site that I had never seen it before. Thanks a lot for the information because I had liked it very much!

Leave a reply