When will OSX be 64-bit ??

[Snowy_River]

So thats a yes to accessing all 8 Gig right?

Does this mean than each up gets access to one of the 2 4gig ram segments rather than free reign to all 8 gig?

I am confused

Yes. The kernel can access all of the RAM (actually up to 16GB, not 8GB, using the largest RAM chips available), and handles handing out RAM space to the apps. Each app is only given access to a 32-bit virtual memory space, or 4GB. Two different apps, however, will be given access to different memory space. So, if you have 8GB of real RAM, the kernel could, in principle, divide that into two separate blocks of 4GB virtual memory space, and hand each of those two blocks to separate apps.

What happens if you don't have 8GB of RAM (or you're on a G4 - not sure about that as I seem to recall that the kernel had access to 42-bit memory access on the G4, but I don't remember where I read that), but have two apps that each want a full 4GB of memory? Well, then your computer starts using a disk cache to provide a larger virtual memory space. This, of course, means massive slow-downs.

So, the question is whether or not you have one or two (or more) memory hungry apps that you'll be using. If you only have one, increasing your RAM much above 4GB is pretty pointless until Apple implements 64-bit memory calls in OS X.

 

[aswitcher]

SNIP

So, the question is whether or not you have one or two (or more) memory hungry apps that you'll be using. If you only have one, increasing your RAM much above 4GB is pretty pointless until Apple implements 64-bit memory calls in OS X.

Thanks, that makes sense. Academic really, I can't afford 8 gigs of ram.

SO in theory Apple could build a new PowerMac with 12 or 16 gigs of ram with the current processors and it would work but they need to match a processor to each 4 gig to do that?

 

[Snowy_River]

Thanks, that makes sense. Academic really, I can't afford 8 gigs of ram.

SO in theory Apple could build a new PowerMac with 12 or 16 gigs of ram with the current processors and it would work but they need to match a processor to each 4 gig to do that?

Not really, no. An app can grab 4GB of memory regardless of whether or not it has processor time to run. A single 1.6GHz G5 can support up to 8GB of RAM and duals can support up to 16GB of RAM, so on duals 4 memory intensive apps could each have 4GB of virtual memory space with little need for a disk memory cache. Of course, they wouldn't see much of the speed up from this, as they'd all be fighting for processor time.

(Currently, Apple only officially supports the 1GB chips, but unofficially, the G5s fully support the new 2GB chips. Of course, these chips are currently obscenely expensive, costing on the order of $1000 each...)

 

[aswitcher]

Thanks. Makes sense. Well I guess we need to wait for those fully optimised apps and the osx 10.? to appear...

 

[leftbanke7]

Thanks, that makes sense. Academic really, I can't afford 8 gigs of ram.

SO in theory Apple could build a new PowerMac with 12 or 16 gigs of ram with the current processors and it would work but they need to match a processor to each 4 gig to do that?

I just read an article that said that the G5 chip can actually handle 4 TB of RAM, however, where would we put all those sticks?

http://www.freep.com/money/tech/sixfor25_20040325.htm

 

[bousozoku]

One important thing to bring up is the definition of 64-bit. In some sense, OS X is already 64-bit. The kernel can address a full 64-bit memory space. However, from the application's point of view, that doesn't help, as Apple hasn't yet incorporated 64-bit memory calls for apps to make. So, apps are currently limited to being able to address 4GB of memory space, max. Who cares, right?

...

So, using the presence or absence of 64-bit memory calls from the OS as the measure of whether or not it's a 64-bit operating system, there is plenty of incentive for Apple to make OS X a 64-bit operating system. While not a trivial step, it's also not as hard as rewriting the entire OS. Also, by this measure, 32-bit applications wouldn't see any change whatsoever in performance...

I went through this with the big machines in the mid-1990s. There was one machine which was completely capable of using 64-bit hardware and that was the IBM AS/400 with OS/400 and the Power PC_AS, which was an offshoot of the PowerPC 620. This is an operating system that was recently configured to have 448-bit virtual hardware, no matter what the real hardware is. If you look back, I think you'll find that the IBM System/38 with CPF was using 128-bit virtual hardware in 1979.

UNIX at that time, was only 32-bit but various vendors would claim 64-bit support because the file system could support 64-bits of something or the operating system could dole out 64-bits worth of RAM, but the operating systems were only declared 64-bits overall years later.

I hope that Apple moves quickly to avoid the original PPC mistakes--strong hardware and an operating system unable to take advantage of it.