processor upgrades Graphics Cards

Zero To 500Mhz In Several Nano Seconds - A Review Of Sonnet's Newest Cache Slot Card

by David Engstrom

General Impressions: Fun, Fun, Fun, is how I would describe slapping the Sonnet Crescendo G3/L2 500Mhz into our Twentieth Anniversary Macintosh and watching it turn from a stately aging Bentley, into a rip roaring Porsche fresh off the factory floor. The performance of the Sonnet card is truly amazing, the engineering tight and well done. Unfortunately the bug that we have documented with previous Sonnet cards in the L2 family, continues in this latest upgrade, marring what would otherwise be a thing of near perfect performance pleasure! [see update below regarding this issue]

Supported Models

Apple: 20th Anniversary Macintosh, 5500s and 6500s

Mac OS 7.5.3 - 9.0 supported

Sonnets Crescendo G3/L2 400Mhz and 500Mhz cards will only work in machines with a 50Mhz bus. Sonnet sells lower speed cards that will work in other compatible machines

For those of you not familiar with the innovation of L2 cache slot G3 upgrades a short explanation is in order. These cards fit into the L2 cache slots of machines previously thought to be non-upgradable because (in most cases) their original processors were soldered to the motherboard. Clever upgrade manufacturers have engineered a way for a G3 card placed in the L2 cache slot to usurp control from the main processor during the boot process. In the case of the Sonnet L2 card, the machine initially boots off the original processor. When the Sonnet software extension is loaded a G3 "environment" is setup and processing power is handed over to the G3 upgrade. This happens almost seemlessly in Sonnet's case - other cards have a double boot process.

Intallation: Installation is straightforward and simple. Sonnet's printed instructions are concise and adequate. If you have ever installed RAM or a cache card you will have no problem installing the Sonnet Card. First you install the software - an extension that enables the card, the LibMotSh extension - LibMotSh is an high performance shared math library that is suppose to improve FPU performance - and Metronome - a utility which, when you run it, will provide you with stats on the installed card, including operating temperature. (LibMotSh can be found as freeware on the Net and can be installed on most machines whether they have a G3 upgrade or not.) After the the software is installed, shut down the machine, and gain access to the motherboard. (How you access the motherboard will depend on the machine that you are working with - consult your manual). Once you have the motherboard exposed touch a metal part of the fan housing to ground yourself - static electricity and your motherboards components don't like one another! You will need to locate the L2 cache and remove it. The manual goes into detail for each model type how to do this and the cache slot should be marked on the motherboard. You will find that the cache card likes being attached to your computer. You will need to pull firmly and consistently to get it to come out. If your cache card has hole on either corner you can hook something in them to help you get the card out. We used a paper clip gently (yet firmly) pulling at one corner and then the other until it popped out. Remember to pull straight up and not at an angle.

Installing the G3 card is easier than pulling the cache card out. On the TAM the heatsink of the card faces the bottom of the machine. Line the card up properly in the cache slot and push firmly on the edge of the card and the upgrade should pop right in. Replace the cover of your computer (if you are using the thin cover on the back of your TAM you will have to migrate to the "Fat" back), restart your machine, use the Metronome software utility (now found in the Apple menu) to make sure everything is working properly. Now head for the fast lane!

Stability And Operation: We installed the Crescendo G3/L2 500Mhz card in a Twentieth Anniversary Macintosh (TAM) for 2 weeks and experienced no stability issues with the upgrade once the machine had booted. However we had problems with the same intermittent startup freezes that we documented so well in a previous review of earlier Sonnet L2 cards. The freezes are random and intermittent and only occur every 6 restarts or so (even that is hard to pin down). It is annoying more than anything, but is usually fixed by a forced reboot.

[Update: Since this review we purchased a Crescendo G3/L2 500Mhz and have been running it in our TAM without incident - it appears that Sonnet has been able to address the startup freezing issue by updating the Crescendo extension. Be sure to download the latest extension version from Sonnet's web site if you are using one of these upgrades]

If you are using Apple's Geoport modem, it is not compatible with this upgrade.

The temperature of the chip during operation ran consistently at 63 degrees celsius - we also have a PCI Ethernet card in our TAM that throws off some additional heat. The PowerPC G3 chip is rated for a maximum recommended opertating temperature of 102 degrees celsius.

One addtional thing about Sonnet processors is that there are no adjustments to make, no dip switches to set, no control panel settings, just stick the processor card in and go. I personally like this simplicity but people that like to tinker with settings to squeeze out every last facet of performance may miss the ability to fiddle.

Performance: We experienced anywhere from a 50% to 500% speed improvement over the base TAM performance, depending on the task being undertaken (see benchmarks below). If you are doing any type of heavy lifting with your Mac the Crescendo G3/L2 500 will provide significant performance improvements and rip though those tasks many times faster than your base machine can. Our photoshop tests showed a 3 to 4 times speed improvement as did our rendering test. However even people that use their machines for simpler tasks will find that a G3 upgrade will make their systems much more responsive and agile as they go about their daily chores. If you have a high-speed Internet connection you will find that a faster machine really makes it come alive. You will realize how much your current processor is choking on all the data your Internet pipe is sending its way.

Some caveats on performance. While a G3 upgrade will rejuvenate an older machine, it will not turn it into a new one. You will still have that old slow hard drive and outdated graphics card - unless you choose to upgrade them as well.

Conclusion: Unfortunately the Sonnet L2 cards are marred by occasional startup freezes - at least in some machines. Because of this problem they did not receive from us the top marks that they otherwise would have gotten. You will have to decide for yourself if top of the line performance is worth this inconvenience. Price is another factor. The suggested retail price for the Crescendo G3/L2 500Mhz card is about $1000 - about the same price as a brand new low end 350Mhz iMac (Since this article was posted Sonnet dropped the price on the card to $799). For TAM owners upgrading your machine is a no-brainer - the TAM is not the kind of machine you turn in for a later model. However for owners of 5500 and 6500 PowerMacs who are just doing general computing you would be better off selling your old machine and opting for one of the new iMacs. If on the other hand you need tons of raw processing power the Sonnet upgrade will provide what you are looking for and then some.

Product: Crescendo G3/L2 500Mhz
Company: Sonnet
Rating: (5 possible)

Hits: Excellent performance, good stability once machine has booted, easy installation

Misses: Occasional freezes during the boot process, expensive

MSRP: $1000 Sonnet has dropped the price on this card to $799

MacBench 5.0 Results






Publishing Disk




"Real World" Tests
(Shorter bars are better)

Time to Scroll a 500 page AppleWorks document from top to bottom.


Using the same document as above we did a search/replace command to replace the word "the" with the word" macbench"


Actual Render Boy Render Times: Crescendo 87 seconds, Base TAM 343 seconds

PhotoShop 5.0.2 "Real World" Test results






Crescendo Card Stats



Cooling System

Variable/Fixed Clock Rate

Tech Support


Price Information

Sonnet Crescendo G3/L2 500/250/1MB

L2 Cache Slot

Heat Sink



3 Years