4GB of memory on 32-bit Mac OS?

[phexac]

So Apple finally started offering 4GB of memory on their computers at a more reasonable price point. However, my impression was that OS X was all 32-bit. Therefore it cannot take advantage of all that memory and Apple is just taking advantage of the fact that most people don't know any of that. What am I missing here?

 

[Kmax82]

Leopard is 64 bit, but not all apps have moved to being 64 bit. The OS can utilize the RAM but the apps themselves can't unless they are 64 bit as well. All the core apps have been ported to 64 bit for Snow Leopard I believe, plus Apple has new frameworks in place to help devs move to 64 bit as well as multithreaded processing. It's similar to how you have a Core2Duo, or Quad, but really can't use all that power, even though OS X/Windows/Linux supports it.

 

[phexac]

Ah ok, didn't know Leopard was 64-bit. Thanks.

 

[Nothinman]

Therefore it cannot take advantage of all that memory and Apple is just taking advantage of the fact that most people don't know any of that. What am I missing here?

Nothing, you're pretty much right. Despite the fact that they've had the "Worlds awesomest 64-bit UNIX workstation available" ads for years the OS wasn't and still isn't 64-bit.

 

[CU]

Snow Leopard will be will be first version with a 64bit kernel.
Good Read.

 

[Kmax82]

While it is a bit tricky. Leopard isn't fully 64 bit, but it will run 64 bit code. Snow Leopard, however, is FULLY 64 bit.

 

[Nothinman]

Snow Leopard will be will be first version with a 64bit kernel.

That's got to be wrong, a 32-bit kernel can't load and run a 64-bit binary.

 

[umrigar]

Leopard 10.5

http://www.apple.com/macpro/features/leopard.html

64-bit power.

Leopard is to the new Mac Pro what a skilled driver is to a car with a powerful engine ? a perfect match. Since the entire operating system is 64-bit ready, you can take full advantage of the 64-bit architecture of the Quad-Core Intel Xeon ?Nehalem? processors inside the new Mac Pro. Add to that the 32GB of memory available for the Mac Pro, and the performance of Leopard is even better than before. Leopard also enables developers to build complete 64-bit applications using the Cocoa, Quartz, OpenGL, and X11 GUI frameworks. And because Leopard supports 64-bit and 32-bit applications, you don?t need a new set of devices or drivers.

Leopard delivers 64-bit power in one universal operating system. Now the Cocoa application frameworks, as well as graphics, scripting, and the UNIX foundations of the Mac, are all 64-bit. And since you get full performance and compatibility for your 32-bit applications and drivers, you don?t need to update everything on your system just to run a single 64-bit application.
Bridge the generation gap.

Since the entire operating system is 64-bit ready, you can take full advantage of the Xeon processors in the Mac Pro and Xserve. You get more processing power at up to 3.0GHz, without limiting your programs to command-line applications, servers, and computation engines.

Driver compatibility.

Because of its universal nature, with Leopard you don?t need a new set of drivers ? or devices. New 64-bit applications work just fine with your existing printers, storage devices, and PCI cards. Even better, if you upgrade to new 64-bit-capable drivers, your 32-bit applications will also benefit from the increased throughput.

64-bit frameworks.

In addition to the POSIX and math libraries supported in Tiger, Leopard enables developers to build complete 64-bit applications using the Cocoa, Quartz, OpenGL, and X11 GUI frameworks. You can even use 64-bit Java on capable Intel processors. And the 64-bit and 32-bit versions of the libraries are built from exactly the same code base, to ensure a consistent experience for both developers and users.

 

[Nothinman]

64-bit power.

Wow, way to drink the Kool-Aid...

 

[ViRGE]

Originally posted by: Nothinman

Snow Leopard will be will be first version with a 64bit kernel.

That's got to be wrong, a 32-bit kernel can't load and run a 64-bit binary.

No, that's right. Leopard somehow ran 64bit binaries on a 32bit kernel, and SL will finally move to a 64bit kernel. It's all rather screwy compared to how Windows and Linux did it.

 

[Parasitic]

Originally posted by: Nothinman

64-bit power.

Wow, way to drink the Kool-Aid...

Vista x64 is the same way. If it were fully and wholly 64-bit only then it wouldn't be able to run x86 applications without some sort of emulation in place.

 

[Nothinman]

No, that's right. Leopard somehow ran 64bit binaries on a 32bit kernel, and SL will finally move to a 64bit kernel. It's all rather screwy compared to how Windows and Linux did it.

No, it's not screwy at all. My mind's a little cloudy from game 6 last night but at the very least a 32-bit kernel can't save/reload the extra GPRs used in long mode so the CPU state would get trashed.

Vista x64 is the same way. If it were fully and wholly 64-bit only then it wouldn't be able to run x86 applications without some sort of emulation in place.

No, Vista64 has a 64-bit kernel and the necessary 64-bit core software in place. Yes, it has 32-bit versions of most of the libraries so that 32-bit code can run but it's still a 64-bit system.

 

[sourceninja]

The kernel has to be 64bit to run 64bit applications. Userpsace can still be 32bit with no problems, but the kernel has to be 64bit for anything to be 64bit.

 

[smokozuna]

Great info, thanks for the education guys!