Sidebar Sidebar
Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.

21.5" won't boot in 64-bit?

B

britboyj

macrumors 6502a
Original poster
Apr 8, 2009
817
1,088
I have the base 21.5" iMac (because hey, if I'd have got a machine with these specs six months ago, I'd have been paying $2400, graphics card aside, which I don't need for anything I do) and no matter what I do, I CANNOT get it to boot in 64-bit mode.

Tried holding down 6 and 4 (unlikely to work since it's a BT keyboard after all) and tried modifying the boot plist. Still nothing. The Terminal command to check 64-bit extensions returns that it SHOULD be okay, but it says 64-bit extensions "no" in System Profiler.

What gives?
 
Does it matter? Not sure what the point would be unless you are trying to access tons of memory.

64-bit mode just enables a 64-bit kernel. I don't think they have all of the extensions in 64-bit yet. You can still run all 64-bit capable apps with the default 32-bit kernel.

according to here, it might not be supported right now.
 
gibbz said:
Does it matter? Not sure what the point would be unless you are trying to access tons of memory.

64-bit mode just enables a 64-bit kernel. I don't think they have all of the extensions in 64-bit yet. You can still run all 64-bit capable apps with the default 32-bit kernel.

according to here, it might not be supported right now.
Click to expand...

It will make your system faster:
http://macperformanceguide.com/SnowLeopard-Performance.html

And the Apple chart be a lot clearer - but you do have a machine capable of using the 64Bit Kernel (at least you should... the 27" is and all current MBPs are... I cannot see why not)

try typing in terminal:

ioreg -l -p IODeviceTree | grep firmware-abi

if it returns '"firmware-abi" = <"EFI64">' you are good to go. It should.

Assuming you got the EFI64 value, type then reboot:

sudo nvram boot-args="arch=x86_64"

NOTE - you will lose this setting if/when you reset your PRAM.
 
RealEvil said:
try typing in terminal:

ioreg -l -p IODeviceTree | grep firmware-abi

if it returns '"firmware-abi" = <"EFI64">' you are good to go. It should.

Assuming you got the EFI64 value, type then reboot:

sudo nvram boot-args="arch=x86_64"
Click to expand...

Is this a better, worse or different than doing it by modifying the plist?

EDIT: Tried this, still no dice. System profiler still says 64-bit kernels and extensions - No. Terminal DID return EFI64.
 
iLog.Genius said:
I don't know if this would prevent it from booting into 64-bit but would you have a firmware password by any chance?
Click to expand...

I don't even know how to do, or check that. When I chance the plist I enter my admin password, same for entering the sudo command in terminal.
 
britboyj said:
Is this a better, worse or different than doing it by modifying the plist?

EDIT: Tried this, still no dice. System profiler still says 64-bit kernels and extensions - No. Terminal DID return EFI64.
Click to expand...

Its no better or worse except that you might reset your PRAM sometimes.

So you got the EFI64 response? But the sudo command did not work (you gave your correct password right)? If those 2 statements are true, I suggest you ask someone else on this forum with a 21.5 to test this too but are you sure you typed it in correctly?
 
Found the problem!

When I started the machine I restored from my MacBook Air's Time Machine backup, which contained two EFI firmware updates for the first-gen Air. Deleting these and resetting the PRAM allowed the iMac to boot in 64-bit. :)

So for those getting new iMac's and transferring from old machines: DELETE YOUR OLD EFI UPDATES FROM THE NEW MACHINE.

Thanks for the help!
 
You must log in or register to reply here.
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.
Top Bottom
Back