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Is leopard a real 64bit OS?


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#41
Konami®

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I wish my Leopard install would be able to use all 8GB I have. I installed 8GB and it wouldn't boot all the way to the desktop...just blue screen with no icons or cursor. Removed a stick of DDR2 and it would boot to the desktop with 6GB installed. About this Mac only recognized 4GB, but System profiler identified all 3-sticks (6GB). Apps like console, software update and the installer app would launch and quickly crash. Removing another stick (4GB total) would give me a more stable system with all apps functioning as they should.

I guess it's an issue with AMD processors and 64-bit addressing under Leopard (or lack there of).


Perhaps your motherboard only support 4GB or the BIOS is configured to support only 4GB.

#42
AppleTalk

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If it's 32 bit why can it address over 4 gigs of ram?


valid point.

Last I read was that portions of the software/utilities included in leopard have not been fully ported to 64bit. but the core kernel I think is or else how can it address more than 3 gb ram...

I guess everyone forgot Steve Jobs demonstration of a 4gb photo running in 32bit vs 64bit app in OSX at macworld 2007 and difference in rendering speeds...unless it was the reality distortion field messing with my mind.. :thumbsup_anim:

http://www.macworld.com/article/58339/2007/06/livekeynote.html

“Number four,” said Jobs. “Leopard is 64 bit from top to bottom.” This is the first time that 64-bit will be mainstream in the computer world, he said — not only does mean Leopard’s Unix underpinnings will be 64-bit, but so will Cocoa.

“One version of Leopard runs 32-bit and 64-bit apps side by side,” explained Jobs. “If you write a 64-bit app, you can guarantee that it will run on every copy of Leopard out there.”

To demonstrate the capability, Jobs loaded a giant photograph — 4GB in size — into a demo application that showed CPU and disk access. One version ran in 32-bit mode, the other in 64-bit mode. Running filters on both systems, the 32-bit version took 81 seconds to complete the tasks, hammering the hard disk in the process. The 64-bit version was able to load everything into memory, and finished in 28.48 seconds.


the other question now is....does the apps come in 2 separate installers like windows for x86 and x64 ? Most 3rd party vendor software don't state whether they run in 64 bit mode or not...which I think alot them haven't ported over to 64bit yet... just wondering.

#43
Ranguvar

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You can address more than 4GiB of RAM if you use PAE: http://en.wikipedia....dress_Extension

For the most part, there is no real benefit to 64-bit CPUs and apps. Only the following...

- PAE comes at a very slight performance loss.
- If you have an AMD64 (I call it this because it's the real name, Intel's EM64T was made to be compatible with AMD64) CPU, they can assume you have features like SSE/SSE2/etc, so they can compile in that ASM. But as we know, Apple is already able to assume all recent Macs have an SSE3 processor.
- More registers. This helps some, but I wouldn't give even a 10% across the board, much less and maybe 10% in some areas (like x264).
- There are some other benefits, but this is more being _able_ to do stuff than do stuff _faster_.

Overall, I say Apple's claimed advantages of 64-bit processing are hokey at best. Whether Snow Leopard has a real 64-bit kernel, I don't know. It's not like it would be terribly hard to make it such. Is that what you mean by 'OS'? Would a 64-bit kernel with everything else 32-bit count as a 64-bit OS?

#44
Nheru

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I know for sure that 32-bit Windows will NOT address (read "use") >3.x Gb. (It's somewhere about 3.2-3.5 Gb depending on how you measure it) From what I understand there has been a limit of 2Gb of addressed space being available to any single application, however that has been fixed through updates and service packs. Also the service packs have served to change how the memory is reported, so if you have 4gb installed, it will "recognize" it all, but it will not address (use) it all.
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Note the "Physical memory available to Windows"

I understand my install of Leo is kinda jacked up as it's modified to run on my AMD, but it doesn't seem there should be much difficulty running the 64-bit code as AMD is the originator of the x86-64 instructions (for once, Intel had to adopt a standard they didn't create). Every item in my "Activity Monitor" shows it's kind as "Intel" (not "Intel 64") but completely recognizing all 4gb of memory. Does that mean my Leo is running the 64-bit extension to address it?

The Kernel is a true 32/64bit hybrid. This is excellent as the drivers from panther/jaguar days still work.Just run the included Chess program and fire up Activity Monitor and look for Chess. It will show up as Intel 64 bit if you have a 64 bit capable processor.

I tried that but it still showed up as just "Intel", not "Intel 64"

#45
riws

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I know for sure that 32-bit Windows will NOT address (read "use") >3.x Gb. (It's somewhere about 3.2-3.5 Gb depending on how you measure it) From what I understand there has been a limit of 2Gb of addressed space being available to any single application, however that has been fixed through updates and service packs. Also the service packs have served to change how the memory is reported, so if you have 4gb installed, it will "recognize" it all, but it will not address (use) it all.
Posted Image
Posted Image
Note the "Physical memory available to Windows"

I understand my install of Leo is kinda jacked up as it's modified to run on my AMD, but it doesn't seem there should be much difficulty running the 64-bit code as AMD is the originator of the x86-64 instructions (for once, Intel had to adopt a standard they didn't create). Every item in my "Activity Monitor" shows it's kind as "Intel" (not "Intel 64") but completely recognizing all 4gb of memory. Does that mean my Leo is running the 64-bit extension to address it?


I tried that but it still showed up as just "Intel", not "Intel 64"

PAE does the memory job for 4GB. You are still 32bit world. AMD's AMD64 and Intel's EM64T are compatible with each other, but not the same 100%, this is with all CPU instruction sets. And your AMD lacks of SSSE3, witch is the main deal here between AMD and Intel 64bit way in Apple's mind.

#46
Superhai

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If you want to be very technical for any OS and PAE, it works with memory up to 64GB. But there is an issue with page tables when using that amount of memory, they have to be in the 32 bit area together with the kernel, and for 64GB I would guess the paging table are around 1.5GB leaving not much left for the kernel. Also physical address space is still 32 bit and for many kind of hw that is required.

More registers may give quiet good boost, but it means it must be used as well, it is no help if you don't recompile the app. I see many knows this, but few knows why and therefore put up wild guesstimates of the performance increase. Anyway registers are storage areas inside the CPU, opposed to in memory where you will find the stack and other memory addresses. Of course if you are lucky you have the memory you want to access in the cpu cache. Memory access must go via the FSB to the memory, you might know your FSB frequency and your CPU frequency, and see the discrepancy. Registers are readily available and do not need any memory transfer, and cache as well are much much faster than memory access.

On the flip-side the cache needs more space in 64 bit operation due to bigger datatypes and 64 bit alignment. So chances for cache misses are higher.

#47
Nheru

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PAE does the memory job for 4GB. You are still 32bit world. AMD's AMD64 and Intel's EM64T are compatible with each other, but not the same 100%, this is with all CPU instruction sets. And your AMD lacks of SSSE3, witch is the main deal here between AMD and Intel 64bit way in Apple's mind.

Actually the chip in my Hack is an AMD Athlon X2 6000+. It's the 125w version and it does have the SSE3. (I linked to Wikipedia as it was quicker and easier than booting to Windows to grab a screenshot with CPU-Z)

#48
eject

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Actually the chip in my Hack is an AMD Athlon X2 6000+. It's the 125w version and it does have the SSE3. (I linked to Wikipedia as it was quicker and easier than booting to Windows to grab a screenshot with CPU-Z)

no, it doesn't have it, ssse3 is no missprint of sse3

http://en.wikipedia.org/wiki/SSSE3

#49
whaase

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Ok, old thread I know. But I'm wondering now, if SL it a true full 64 bit os, does it run all 32 bit apps?

#50
Ranguvar

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If it were, yes it would.
64-bit operating systems can run 32-bit apps just fine. The problem is running 32-bit apps that require certain libraries, because those libs must also be available in 32-bit form, but MacOS, Windows, and most GNU/Linux distros handle that gracefully.

#51
GrootWitBaas

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I found this to share with you guys.

http://events.ccc.de..._osx_kernel.pdf


From this file :

The OS X kernel is not 64 bit. It supports 64
bit user mode applications on a 64 bit PowerPC
or Intel CPU, but the kernel itself runs
in 32 bit mode and is bound to the 4 GB address
space limit.

So to answer the original post of Envying ....and he has done this himself already ....Yes,

Kernel is the core of an OS, Mach_kernel is a universal binary file using ppc & i386(not x86 64) instructions... So can I say Leopard is not a real 64bit OS!



for now...... :hysterical:

That probably explains why my vanilla install (using 10.6 retail) fails with more than 4GB

#52
thomsn

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Ist it a 4GB or the 3 to 3,5 GB limit?

#53
andarion

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It's not a 64 bit OS, it's a 32 bit OS that you can run 64 bit applications on.





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