10.4 64 bit my G5 64 bit what does this mean?

[jayscheuerle]

You guys laid it out way better than my ignorant, but basically correct post.

If anyone wants to know more, this is from Apple's site:

What 64 bit means...

 

[broken_keyboard]

Indeed, but that's what I'm having a hard time understanding. To my mind, if the compiled application knows to throw 64-bits at the processor at a time instead of 32, how could that be anything other than a faster way to process instructions and data? Admittedly, given the notion of bottlenecks getting 'filled to capacity' probably not twice the processing speed, but certainly faster than the 32-bit version.

It would require an application written to work in a 64-bit environment and for Tiger to support it, but I don't see how this would not improve performance on a G5 system as and when the software exists.

Clearly I'm missing something!

You are thinking that ultimately, at the physical level, a 32 bit program executes like this:

modify 32 bits
modify 32 bits
modify 32 bits
modify 32 bits
done

And therefore the same program can be rewritten on a 64 bit CPU like so, and go twice as fast:

modify 64 bits
modify 64 bits
done

What you are missing is that programs are not actually executed at that low of a level. They are executed at this level:
ADD AX, 1
XOR BX, BX
JMP 12
...

With each of those operations (ADD etc.) physically wired on the CPU. So programs are too chunky to take advantage of the extra bandwidth in the way you hope.

 

[za9ra22]

Again, thanks for taking the time to explain - it actually does make sense the way you have (collectively) explained it.

 

[spaceballl]

64bit is not faster than 32bit.

No but if you take a program that uses lots of large numbers (intense 3D games, graphics programs, etc) and re-code it to take advantage of 64bit then it is often quite a bit faster.
-Kevin

 

[Eric5h5]

Again, thanks for taking the time to explain - it actually does make sense the way you have (collectively) explained it.

Very cool. Unfortunately, a few weeks from now this same topic will be posted again by someone who wants to know why their (semi) 64-bit Tiger isn't running twice as fast as 32-bit Panther. And again, and again...darn 64-bit marketing! But at least now you can help in the explanations if you want.

--Eric

 

[Orlando Furioso]

my head hurts.

 

[Kelmon]

Virtual Memory

It might be worth noting that in terms of addressing more than 4GB of memory, you don't actually need to have that memory physically present in your G5 system. The movement to 64-bit allows applications to address more than 4GB memory but it will be virtual addresses that are mapped to space in your physical memory and swap space on the hard disk. As such you don't need more than 4GB of physical memory to allow your 64-bit applications to use more than 4GB, although as much RAM as you can get will help if the application has such demands.

It's interesting to note that when you look at the Activity Monitor that you applications are using way more RAM than you have available. I have 1GB in my PowerBook but yet my applications (and there aren't many open) have a combined virtual memory usage of approximately 7GB, although none currently use more than my physical RAM limit. For most applications it is unlikely that the removal of the 4GB addressing limit will make much impact (Word is unlikely to need more than 1GB, hopefully) but 3D, scientific and database applications should love the increase.

Personally, I'm expecting 64-bit computing to make bugger-all difference to my day-to-day computing experience.