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Perhaps you've recently upgraded to Mac OS X, and you notice your once acceptably fast blue-and-white Power Mac G3 beginning to show its age. Luckily, this Mac's 100MHz system bus makes it a prime candidate for a processor upgrade, which can give you nearly top-of-the-line performance. Macworld Lab examined PowerLogix's 450MHz PowerForce G4 ZIF card; Sonnet Technologies' 400MHz and 500MHz Encore ZIF G4 cards; and XLR8's 400MHz, 450MHz, and 500MHz Mach Speed G4 ZIF MPe cards. We found that although these cards performed similarly (relative to their speeds), those from Sonnet and XLR8 offered the most extras.
G4 or Not G4?
A G4 processor has a subprocessor called AltiVec (Apple calls it the Velocity Engine), which can dramatically boost performance--but only in applications designed to take advantage of it (such as Adobe Photoshop and some other image-editing programs, MP3 encoders, and video-editing packages). Not many applications are optimized for AltiVec, but if you happen to work with one of them every day, you'll want a G4. And Mac OS X uses the Velocity Engine much more than Mac OS 9 does, so if you're planning to switch to OS X, a G4 upgrade may be in order.
Anatomy of an Upgrade
A G4 processor cannot work in a blue-and-white Mac without a firmware patch, which modifies the ROM, preparing the motherboard for the upgrade. But only Sonnet provides a method for removing the patch; you would have to contact the other companies for a removal procedure (at press time, each was developing this procedure and was hesitant to release it).
XLR8 had the best installation package, providing all of the necessary tools and excellent instructions. Sonnet's instructions were also very well written--especially for users with little experience inside a Mac--with clear, descriptive illustrations and a minimum of jargon.
Controlling the Cache
Each card has a 1MB L2 cache that, by default, runs at half the processor's speed. (The L2 cache stores frequently used instructions, allowing the processor to operate with greater efficiency.) All the cards come with software that monitors the cache, but the amount of control provided differs from company to company. PowerLogix and XLR8 provide control panels, but XLR8's gives you more control over the cache's speed and other performance parameters. Additionally, XLR8's control panel checks the cache and sets it to the fastest possible settings (even if they exceed the default settings) automatically and reliably. Sonnet's software is invisible to the user and sets the cache settings to the proper speed during startup. If you don't intend to experiment with overclocking--driving the cache to a higher speed than is recommended, to squeeze out more performance--Sonnet's arrangement will be preferable.
Pedal to the Metal
XLR8's 450MHz Mach Speed G4 ZIF MPe had a slightly better Speedmark score than PowerLogix's 450MHz PowerForce G4 ZIF; however, the difference was negligible--the Mach Speed beat the PowerForce by only a second when performing a Gaussian blur in Adobe Photoshop, and it even fell a few seconds behind when encoding an MP3 in SoundJam. The performance of both 450MHz upgrade cards was close to that of the 450MHz Power Mac G3 in our Speedmark and Quake III tests, but the upgrades' speeds far exceeded the G3's when it came to Photoshop, which is optimized for the G4.
The Speedmark subtest that looked specifically at disk speed confirmed that the Power Mac G4, with an ATA/66 controller and a newer hard drive, has much better disk performance than the blue-and-white Power Mac G3, with its slower SCSI hard drive. (The faster disk is part of the reason that the 466MHz Power Mac G4's scores were better than those of the 500MHz upgrade cards.) Even if you upgrade your G3 and your hard drive, you'll be limited by the slower ATA bus.
The upgrades from XLR8 are multiprocessor enabled (MPe). If you purchase a 400MHz MPe ZIF, you can use it as one of the processors in XLR8's multiprocessor upgrade.
Macworld's Buying Advice
XLR8's upgrades come with all of the tools you need, and its products can later be incorporated into a multiprocessor upgrade. Sonnet's good documentation and low prices make its upgrades exceptionally attractive. And software that works without intervention, along with easily removable firmware patches, makes Sonnet's upgrade cards excellent choices for those who don't enjoy tinkering with their machines. The 400MHz cards from these two manufacturers are sensible investments. However, the prices of the faster cards begin to approach those of used or refurbished Apple G4s, which have faster hard drives and CD-ROM drives. The G4 upgrade card from PowerLogix is technically sound, but it has no distinguishing features, and its rough documentation makes it less appealing than the others we tested.