Processor Speed Isn’t Everything

Buying a Mac is a balancing act, with your budget and your needs at opposite ends of the seesaw. How fast a Mac do you need? Is it worthwhile to spend more for a faster processor? And should you spring for the latest dual-processor Power Mac?

Each of these questions has the same, unhelpful answer: It depends. Computer marketers would have you believe that processor speed alone determines performance. The truth is, performance depends on numerous factors--the speed of your hard drive and graphics circuitry, the amount of memory you have, the software you use and even your control panel settings.

If you’re performing basic productivity tasks--Web browsing, word processing, simple spreadsheet analysis--you may now skip to the Sports section: Any Mac will deliver the speed you need. But if you’re manipulating digital images, editing video and audio or creating 3-D graphics--tasks for which Macs are particularly popular--read on to get the most bang for your bucks.

I recently spent several days with stopwatch in hand, measuring the performance of two Power Macs: the 733-megahertz model that sat atop the Mac line last month and the dual 800-MHz model that currently holds the summit. A slightly revamped version of the 733-MHz model is now the entry-level Power Mac; it sells for $1,699. The dual 800 sells for $3,499. In between them is a $2,499 model containing one 867-MHz processor.

Is the second processor worth the extra price? Here comes that answer again: It depends. In my tests, the Adobe Photoshop graphics program was only slightly faster on the dual 800. What really affects Photoshop’s performance is memory: A 733-MHz Mac with 512 megabytes or more of memory often will be faster than a dual 800 containing just 256 MB. So for Photoshop use, consider buying a Mac with a single G4 processor and using the money you save to add memory and perhaps a second hard drive, which also speeds Photoshop. (Adding memory is a great way to speed up any Mac.)

With Apple’s Final Cut Pro video-editing software, however, two processors are unquestionably better than one. On my test track, Final Cut Pro rendered complex video effects about 61% faster on the dual 800, and the entire program was more responsive. Other programs that greatly benefit from multiple processors include video-compression utilities such as Discreet’s Cleaner 5, audio programs such as Mark of the Unicorn’s Digital Performer and 3-D rendering programs such as Alias Wavefront’s forthcoming Maya.

Apple’s iTunes music program also is designed to take advantage of two processors, but in my tests, the dual 800 was slower than many other Macs I’ve tested, including the PowerBook G4 and even the Flower Power iMac. It turns out that the dual 800’s SuperDrive DVD burner isn’t able to read audio CDs as quickly as the optical drives in many other Macs. So although the dual 800’s processors can rip a track faster than any other Mac, they’re hamstrung by a relatively slow drive. It just goes to show how a computer’s performance is determined by numerous components.

The murky waters of performance become muddier still with Apple’s Mac OS X. In OS 9, a program must be specially written to take advantage of multiple processors. That’s why you see dramatic speed advantages with programs such as Final Cut Pro (which is designed for multiple processors), but little or no advantage with programs such as Microsoft Word (which isn’t).

Mac OS X, however, is multiprocessor-savvy at its core. In a dual-processor system, Mac OS X can allocate each processor to a different program, even if those programs weren’t written to exploit two processors. The result, Apple says, is a more responsive system. In practice, I wasn’t able to discern dramatic performance differences between the 733 and dual 800 Macs when running OS X. But that may soon change: Apple says OS X version 10.1, due out later this month, will take better advantage of multiple processors.

Jim Heid is a contributing editor of Macworld magazine.