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Call them "Upgrade-Challenged" Macs: consumer-oriented Power Mac systems, circa 1996 and 1997, that were never intended for CPU upgrades. The most popular systems, based on PowerPC 603e CPUs, were Apple's Performa 6400, Power Mac 6500, and Twentieth-Anniversary Macintosh, but the list also includes Macintosh clones from Motorola and Power Computing. With a fat CPU soldered in place, there doesn't seem to be much of a way to add a G3 chip to these machines.
But waitthose clever upgrade folks have figured out an ingenious way to get near-G3 performance from old 603e Power Macs. Sonnet Technologies, Newer Technology, and PowerLogix have released G3 upgrade cards that fit in the Macs' L2 cache slot. Remove the L2 cache card and pop in one of these upgrades, and you'll soon be racing along at 300MHz or more.
Macworld Lab tested five G3 cards that fit into the L2 cache slot: three Crescendo G3/L2 models from Sonnet and two Maxpowr G3 L2 models from Newer. One Sonnet card features a 400MHz G3 CPU; the others have 300MHz CPUs with a range of cache speeds and sizes. The Newer cards are both 300MHz, but one, the Maxpowr G3 L2 300/1MB, was a hand-built preproduction model; we included it in our tests as a preview, but we didn't rate it because it wasn't shipping at press time. The PowerLogix cards didn't arrive in time for testing.
It was impossible to test the cards in every supported model, so we chose a Performa 6400 with a 180MHz 603e CPU. Other supported Macs include the Power Macintosh 4400, 5400, 5500, 6400, and 6500; the Performa 54XX and 6360; the Twentieth-Anniversary Macintosh; Power Computing's PowerBase desktop; and Motorola's StarMax 3000 and 4000.
We found that the cards do indeed deliver speeds approaching that of a 300MHz G3 system, especially when performing such CPU-intensive tasks as 3-D rendering. The speed boost is apparent not only from our benchmark testing; the Performa also feels peppier with the upgrade cards installed. But as with any CPU upgrades, be prepared for some gotchas, especially considering the upgrade-challenged nature of these Macs.
How do you achieve G3 performance in an old 603e system? The L2 cache in those systems normally serves as a form of high-speed memory, feeding frequently used data into the 603e CPU. The G3 upgrades replace this memory with a fully functioning PowerPC G3 CPU running at 300MHz to 400MHz. In addition to the card, you install a system extension that directs all traffic from the main CPU to the L2 cache slot. Because the G3 processor includes its own backside cache, you won't miss the L2 cache card.
There is a limit to the performance you can get from an older Mac system, however, and these cards push right up against it. Much of the problem lies in the system bus: most of the upgrade-challenged Macs, including the Performa 6400, have a 40MHz bus. By comparison, Apple's iMac and PowerBooks have 66MHz buses, and the latest blue-and-white G3s' buses zip along at 100MHz.
But you don't just miss out on the latest bus speedsthe CPU speed of these upgrades is limited to eight times the system-bus speed. With a 40MHz system bus, your CPU maxes out at 320MHz. Obviously, it doesn't make much sense to get a 400MHz G3 upgrade. As we found in our testing, the 400MHz card delivered only marginally better performance than the 300MHz upgrades, and it sells for a premium. However, if you have one of the supported Mac models with a 50MHz busthey include the Twentieth-Anniversary Macintosh and Power Mac 5500 and 6500you'll see performance closer to what you'd expect from a 400MHz CPU.
Installing these upgrades is theoretically as easy as adding an L2 cache card. However, the cache slot was never meant to host a CPU, and the cards are much bulkier, in every dimension, than the cache cards they replace. The result, at least in the Performa 6400, is a tight fit.
Curiously, the Sonnet and Newer cards place the CPU on opposite sides. When you install the Sonnet upgrades, the heat sink fits snugly against the nearest RAM card; with the Newer upgrades, the heat sink almost brushes against the nearest of two PCI cards (if a card is installed). The Sonnet card is bigger but seems to fit better. However, both companies' cards installed with minimal fuss considering the tight quarters.
Software installation is a breeze. With each card, you just copy an extension to the System Folder and you're ready to go. Both Sonnet and Newer include software utilities that let you gauge your system's performance, and Sonnet's Metronome utility displays the CPU temperaturea concern given the tight fit. However, none of the cardsincluding two that we ran for days without shutting downappeared to cause heat-related problems.
We tested the cards by running MacBench 5.0 and MetaCreations' Bryce 4 in Mac OS 8.6. All five cards showed hefty speed increases over an unaccelerated Performa 6400, but the difference was especially noticeable in Bryce 4: the upgraded system took 40 to 49 minutes to ray-trace a 640-by-480-pixel scene, whereas the native 180MHz 603e CPU took nearly 3 hours.
The MacBench numbers were impressive but not quite as dramatic; even the slowest cards clocked Processor and Graphics scores close to those of a 300MHz beige Power Mac (see "Cards Meet Upgrade Challenge"). As you might expect, the upgrades provided only a modest boost to the MacBench Disk scores.
Even with a maximum speed of 320MHz, Sonnet's 400MHz upgrade (which features a 1MB backside cache) received the highest Processor score. However, unless you have a Power Mac with a 50MHz busallowing you to take full advantage of the CPU speedit's hard to justify the $600 price tag. (Newer's 400MHz upgrade, which we did not test, costs $779.)
The other cards, all with 300MHz CPUs, showed little variation in performance. The primary difference is backside-cache size; Sonnet's 1MB cache version actually bested the 400MHz card in our rendering test, although Newer's card, a preproduction model with a 200MHz 1MB cache, was 4 to 5 minutes slower.
Not surprisingly, the cards showed the greatest variation in MacBench Processor scores, a measure of pure CPU speed. Here, the 400MHz card slightly outpaced the 300MHz G3 reference system and ran more than 30 percent faster than the 300MHz cards with 512K caches. However, all of the cards received similar Graphics scores.
None of the cards appeared to cause any unusual software conflicts or system crashes, but there's no guarantee that the cards will work perfectly with every Mac configuration. And it's unclear if these or any G3 upgrades will support Mac OS X.
Because upgrade vendors have to struggle to differentiate their products, Newer offers a handy antistatic wrist strap for card installation and a two-year warranty. Sonnet offers a better manual and a three-year warranty. Sonnet also dropped its prices in August, giving its cards a definite price advantage. However, there's a common pattern in the upgrade business: when one company reduces its prices, the others inevitably follow.
Add one of these cards, and you'll be convinced that your old consumer Mac has been taking steroids. The performance boost is especially dramatic with rendering or other CPU-intensive operations. Sonnet's 400MHz card generally offers the best performance, but it makes sense only if your Mac has a 50MHz system bus. Of the remaining cards, Sonnet's $299 Crescendo G3/L2, with its 512K, 150MHz cache, gives the best combination of price and performance. However, if you plan to do a lot of rendering, the 1MB cache version may be worth the extra $100 outlay. The Newer cards offer comparable performance, but their prices are much higher than the Sonnet cards'.
Of course, the eternal question remains: Should I upgrade or should I buy a new system? Our standard upgrade advice applies here: If you have a big investment in memory and peripherals for your current system and can live with the inevitable performance bottlenecks, then an upgrade makes sense. But if you don't have a huge investment, and you're ready to step up to the next generation of Mac computing, then you're probably better off with a new iMac or Power Mac system.
|G3 Upgrade Cards Compared|
|$449||316/943-0222||Decent performance.||Expensive; tight fit.|
Requires 50MHz bus for maximum performance; tight fit.
|$399||800/786-6260||Good performance; decent price.||Tight fit.|
|$299||800/786-6260||Decent performance; good price.||Tight fit.|
November 1999 page: 40