Multiprocessor Upgrades: Twice as Nice?

Without much fanfare, all three of the Mac platform's big upgrade card makers have stepped up their efforts to double your Mac's processing power. Sonnet Technologies and XLR8 have already begun shipping upgrade cards that feature two processors instead of one. And PowerLogix is working on a multiprocessor card of its own.

The idea behind these dual-processor upgrade cards is the same notion that prompted Apple to release a multiprocessor system of its own last year-two CPUs are better than one. What's more, the arrival of OS X means the Mac finally has an operating system that can take advantage of multiprocessing. Thus, card makers have a greater incentive to ratchet up production.

Sonnet was the first to market with its Encore/ST G4 Duet card. The $1,000 card features two 500MHz G4 processors, each with its own 1MB of backside cache. Duet works in "Sawtooth" Macs-G4s with AGP graphics and G4s with gigabit Ethernet. Essentially, the Duet replaces the original processor daughtercard in your Mac. Because of this, the Duet requires no software; it's also compatible with Mac OS X.

While the Duet is an elegant upgrade, it only works in the Sawtooth-equipped Macs manufactured since late 1999. While Mac performance has spiked enough since then to make upgrade cards like the Duet commercially viable, Sonnet is looking into developing multiprocessor upgrades for even older Macs.

"We are selling a few more Duets than we expected," said Karl Seppala, Sonnet's director of marketing. So Sonnet is planning OS X-supported multiprocessor products for earlier Zero Insertion Force (ZIF)-based Macs-a type of processor packaging found in blue-and-white G3 machines-and PCI Macs such as the 8500 and 9500 series.

While Sonnet plans to expand its multiprocessor efforts, XLR8 began shipping the first portion of its ambitious multiprocessor upgrade product line this month. XLR8 has based its latest upgrade cards on both ZIF processor packaging and the company's Carrier ZIF product to allow for upgrades in a wide variety of PCI Macs.

XLR8 has created a modular approach for using ZIFs to upgrade Macs. The company began labeling all of its ZIF upgrades last summer as multiprocessor-enabled, or MPe. To get the best performance from multiple G4s, a number of extra physical connections that aren't necessary for a single processor must be made. However, this drives up production costs, so no ZIF packages other than XLR8's have done this-not even Apple's.

Once XLR8 had its G4 ZIF cards enabled to serve as multiprocessors, the company had to find a way to put two CPUs in a single processor slot or ZIF socket. XLR8 came up with two methods, each for a different family of Macs.

For PCI Macs such as the 8500 and 9500, XLR8 created the Carrier ZIF MPe. This approach attaches to the company's MACh Carrier G4 MPe upgrade card, which has one ZIF socket and one Light Insertion Force (LIF) socket. LIF is similar to a ZIF, but with no lever. You choose what speed the G4 in the LIF socket is. You also can choose to buy another G4 for the ZIF socket or buy the card with the ZIF socket empty.

For ZIF-based Macs like beige G3s, blue-and-white G3s, and early PCI G4s, XLR8 offers the MACh Velocity G4 MPe upgrade card. This card works much like the MACh Carrier G4 MPe-it has LIF and ZIF sockets, and you choose how to populate them. The difference? You don't need a Carrier ZIF MPe, but you do need the proper speed MACh Velocity G4 MPe. For instance, if you have a beige G3, you need the MACh Velocity G4 MPe 66 (66 for this Mac's 66MHz bus). Blue-and-white G3s and PCI G4s with 100MHz busses need the MACh Velocity G4 MPe 100.

You can add any ZIF processor to the empty slot in XLR8's MPe carriers. And that's a key selling point for this particular upgrade method: you can use whatever old processor you were already using, or you can buy one XLR8 G4 MPe ZIF upgrade now and put that into a multiprocessor upgrade later.

Still, there are some drawbacks if you use a G3 processor on a non-MP-enabled G4 in XLR8's multiprocessor upgrades, XLR8 Director of Engineering Chris Cooksey says. Use a G3 processor in the empty ZIF socket, and you'll lose all of the AltiVec capabilities of the G4 that came with the multiprocessor upgrade. If you use a non-MP-enabled G4, you'll get AltiVec-the subprocessor technology that speeds up certain applications. But you may also experience slower performance, since non-MP-enabled G4s lack the extra connections needed for superior performance. That also happens if you use a G3 and G4 as your two processors, since the G3 doesn't have these connectors at all. For best multiprocessor performance, XLR8 recommends two of its G4 MPe processors.

XLR8 began shipping the MACh Velocity G4 MPe 66 earlier this month. The Carrier ZIF MPe and MACh Carrier G4 MPe for PCI Macs should ship in about two weeks. The MACh Velocity G4 MPe is still about six weeks out. Prices for these products range from $650 to $1,450, depending on how many processors you're buying and what speeds they are. XLR8's G4 MPe ZIF upgrades currently range from 400MHz to 500MHz.

PowerLogix was one of the first companies to make noise in the multiprocessor arena. The company showed off a multiprocessor design at the 2000 Macworld Expo in San Francisco. Since then, however, PowerLogix hasn't shipped any multiprocessor upgrades.

The company is still working on multiprocessor upgrade cards, says Director of Marketing Robin Sharp-Howdershelt. "We will probably first announce an MP ZIF processor upgrade and a dual-processor upgrade for AGP Macs," she says. "There probably will be no MP PCI upgrade, as this will likely be too expensive for owners of these Macs." Look for news from PowerLogix at the next Macworld Expo in July, Sharp-Howdershelt adds.

Multiprocessing is definitely a high-end technology. In most cases, users will only see a significant performance benefit when using applications that have been optimized for multiprocessing.

Still, one of the oft-forgotten benefits of multiprocessing is the ability to run multiple applications at once. If you routinely jump between two or more applications and find your Mac's performance wanting, you may see a significant boost from a multiprocessor upgrade.

With OS X finally here, many of the factors that held back multiprocessing performance have been removed. OS X's preemptive multithreading and preemptive multitasking give it a distinct multiprocessing performance advantage over the classic Mac OS. If OS X is making you consider a processor upgrade to your Mac, perhaps you may want to consider adding a multiprocessor card instead of a single CPU. It costs significantly more, but if you use applications that tax your Mac or run multiple applications at once, two processors may indeed double your pleasure.

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