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Until today, the one and only time Apple released a Mac with more than one processor inside was 1996, when the company released a power-mad Power Mac 9500. It had two 180MHz PowerPC 604e processors, and to really take advantage of the second one, you'd need to use software specially written for the task.

With the announcement of Apple's two new dual-processor-bearing Power Mac G4 models (at the same prices as the company's original one-processor counterparts), Apple has gone back to the future. With G4 processors running at 450MHz or 500MHz, these new Power Macs are surely speedier than the multiprocessor Mac of 1996. Don't start adding two 500MHz G4s together and coming up with a gigahertz, though: the Mac OS of today still isn't multiprocessor-savvy enough to tax both processors to their limits.

But unlike that evolutionary dead end of four years ago, the placement of these new dual-G4 Macs firmly in the Power Mac product line shows that this latest permutation will stick around. Multiprocessor Macs are back, and this time it looks as though they're here to stay.

The New Boxes

With these new Power Macs, Apple is pushing the Power Mac G4 minitower up into the high end. The base configuration remains the same -- you can still get a stripped-down Power Mac G4 at 400MHz, with a 20GB drive (running at 5,400 rpm, not the faster 7,200 rpm drives found in the multiprocessor models) and 64MB of RAM. But beyond that, the Power Mac minitowers are all about dual processors.

In the middle of the line sits a G4 with two 450MHz G4s. Apple's standard configuration for this model includes 128MB of RAM and 30GB hard drive. And high atop the mountain stands the new Mac speed king, a dual 500MHz box loaded with 256MB of RAM and a 40GB drive.

Mach Speed Ethernet Just as Apple broke new ground by rolling out 100BaseT Ethernet as a standard feature with the original iMacs, the company is again pushing networking to a higher standard with these new Power Macs. Gigabit Ethernet -- that's 1,000BaseT, or speeds 100 times faster than conventional 10BaseT Ethernet -- is standard on all these models, making them primed for any network environment requiring the high-speed transfer of large graphics or multimedia files.

Multiprocessing 101

The real change with these new Macs is the addition of a second G4 processor. Because of the way Mac OS is designed, adding a second processor doesn't actually double your processing power. That's because the current version of Mac OS was never really designed to be run on more than one processor.

In 1995 and with Apple's blessing and cooperation, clone maker DayStar Digital developed a system extension, nPower, that let the Mac OS work with multiple CPUs when you run programs designed for multiprocessing, and became the first company to ship a multiprocessor Mac. Users of Adobe Photoshop, for example, could benefit -- even today, owners of multiprocessor Macs can take advantage of a Photoshop's multiprocessing support to speed roughly 300 different commands, from filters to color corrections. Other early benificiaries of the technology included software from Elastic Reality, Insignia Solutions, Live Picture, Macromedia, and Strata. But the Finder, which was clueless about the extra processors, saw no benefit -- one processor had to do all the work.

Apple licensed DayStar's technology and made it the basis of the Power Mac 9500 MP, as well as integrating it into the Mac OS. But when the PowerPC G3 processor hit the scene, the Mac multiprocessor market stagnated.

The G3 Loner Unlike the PowerPC 604 chip, which could do multiprocessing, the PowerPC G3 is unable to play well with others. As a result, Macs had to go it alone -- and Mac users had to decide between sticking with a gaggle of slower chips or one single fast G3.

However, the G4 processor is able to act in tandem with others of its kind, and Apple set the stage for its announcements today by tuning up Mac OS 9 to work better with multiprocessing systems. (Prior to the OS update, multiprocessor users couldn't use Virtual Memory, among other quirks.) Although we originally reported that the Finder was also helped by additional processors, Apple Hardware Chief Jon Rubenstein confirmed to us that, in fact, Mac OS 9, Finder is completely unable to take advantage of the Power Mac G4's second processor.

The Big Break The fact is, while these new multiprocessing Macs will make killer machines for Photoshop users, they won't dramatically transform the entire Mac experience until the advent of Mac OS X. Unlike the current Mac OS, Apple's new operating system can innately use multiple processors, splitting out all the duties of the computer with ease. On a Mac running OS X, two 500MHz processors really could make you feel as if you're running at 1 gigahertz, because the system will be able to push both of those processors to their limits.

The Last Word

If you're a Photoshop user -- or the user of any other program that shines when using multiprocessing -- these new systems will blow you away. For the rest of the Mac users out there, the advantages are a bit more subtle right now. But when Mac OS X arrives, the performance boosts that these new Power Mac G4s will experience will be gigantic.

Power Mac G4 400MHz Power Mac G4 450MHz x2 Power Mac G4 500MHz x2
Processor 450MHz G4 Two 450MHz G4s Two 500MHz G4s
Memory 64MBB 128MB 256MB
Hard drive 20GB (5,400 rpm) 30GB (7,200 rpm) 40GB (7,200 rpm)
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