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Mac G5's 64-Bitness: What's In It For Me?

More RAM for now, even more speed later By Charlie White

Apple's Mac G5 64-bit processor
It's been nearly a year since Apple rolled out its groundbreaking new personal computer, the G5. A 64-bit platform, the G5 uses one or two of IBM's PowerPC 970 chips, and adds more than just faster chips to the mix. In this article, we'll take a look at what 64-bit computing means for Mac video editors and content creators, how it works, and see what software is taking advantage of this new capability.

What does the term "64 bit" mean, anyway? Think of the data flowing through your computer's components as cars on a highway. The 32-bit highway is half the width of 64-bit, so a 64-bit highway can accommodate twice as many cars going the same speed. But that only tells part of the story. What really makes the difference in computing is the number of possible combinations of that data, and there are far more than double possible with this new wider pathway. When you're talking about 32 bits, that translates into 4GB of data that can be handled at once, or more than 4.29 billion combinations. Move up to 64-bit processing, and then the number of combinations is so high it's hardly comprehensible -- 16 exabytes, or 16 quintillion (that's a 16 with 18 zeros) possible combinations of data (see table below). That's the theoretical limit of RAM that's possible with 64-bit computing. Sounds crazy, but then 4GB sounded like an astronomical number when 32-bit computing was coming into its own at the beginning of the 1990s.

To give you an idea of the amount of data that's addressable by 64 bit computing compared to its comparatively measly forebears, take a look at the following:

Address size Addressable Space
8 bits 256 bytes
16 bits 64,000 bytes
32 bits 4,000,000,000 bytes
64 bits 16,000,000,000,000,000,000 bytes

That's an exciting theoretical construct, but Apple's G5 isn't able to handle 16 exabytes of RAM just yet. Apple vows to support 4 TB of data someday, but for now, we'll settle for the 8GB of RAM that's supported in current G5s thus far. Here's where the biggest benefit of 64-bit computing on the Mac can be enjoyed by G5 users, because Mac OS X 10.3 (Panther) is able to use the entire amount of RAM, up to that limit of 8GB installed on your system as a fast cache or buffer for file system and virtual memory access. Even though the latest OS X Panther is still a 32-bit operating system, it's a key component of Apple's 64-bit strategy. Panther doesn't contain fully 64-bit code, but it still allows some of the strengths of 64-bit processing to shine through. Even though users are able to access all 8GB of RAM at this point, each application under OS X Panther is still limited to the 4GB of RAM that's the limit with 32-bit computing. However, Panther will allow users to run two applications which are each accessing, say, 4GB of RAM each at the same time, totaling 8GB. This would allow users to work with a 4GB file in Photoshop while also scrubbing a 4GB video file in Final Cut Pro, for instance. Regardless of the application being used, that extra RAM will give editors and graphic artists the ability to hold huge files in RAM, where before they needed to access this data on a swap file that transfers that data at 1/40th the speed of data that's sitting in RAM. This translates into the ability to smoothly scrub through huge video files, for example.

Another factor that offers a welcome speed-up for video editors, particularly those who are editing huge high definition video files, is the increased input-output (I/O) volume that's possible with 64-bit architecture. Increased system performance of hard disks and video cards are what the doctor ordered when it's time to edit video, and as soon as there are applications written to take advantage of all this new-found bandwidth, video editors can expect to see significant benefits. As it stands now, any application that processes large amounts of data -- such as Final Cut Pro, Photoshop, mathematical apps, DVD authoring, especially if its individual files exceed 4GB -- stand to gain from the 64-bit kernel in OS X Panther. Speeding up the proceedings even further is a new 1GHz frontside bus employed in the new G5 architecture, compared to the 167MHz bus speed of its predecessor, the Mac G4. This allows much faster throughput, at speeds of 16GB per second.

You've probably already figured out that this 64-bit computing would be extreme overkill for everyday desktop computer users, but when it comes to graphics and video production, anything that will allow content creators to use more RAM is a blessing, that is, if they can afford to pay for that 8GB of RAM. That's no small order, either -- if you order 8GB of RAM on Apple's Web site today along with your G5, that'll run you an extra $4650 over the standard 512MB of RAM.

Even if you don't go for a full boatload of RAM, another key benefit of the new G5 chip is its backward compatibility with 32-bit applications, a crucial attribute since nearly all the installed base of Macs are running 32-bit software. Still, the G5 chip can run 32-bit code faster than its G4 predecessor, in part due to the G5 chips' higher clock speeds (Dual 2GHz is the top of the G5 line, where dual 1.25 GHz is the fastest currently-available G4) and also due to the re-vamping of the OS X code to take advantage of the new chips.

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Related Keywords:Mac G5, 64-bit computing, Charlie White, Apple, personal computer, platform, IBM, PowerPC 970 chips, video editors, content creators, how it works, 64-bit software

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