October 25, 2002

by David Engstrom

The Harmoni is Sonnet's current upgrade for the original iMacs. This includes versions A-D. These iMacs clocked in at 233 MHz, 266 MHz or 333 MHz, and all had a G3 processor. If your iMac has a tray loading CD drive, you have one of these iMacs.

The Sonnet upgrades come in two speeds, a 500 MHz version and a 600 MHz one. They also sport the G3 processor, but the Harmoni only comes with 256K of backside cache, whereas the iMacs original processor cards came with a more spacious 512K. As you'll see from a few of the test results below, the fact that the Harmoni's backside cache is half that of the original processor did have some minor effects on performance, and in other cases retarded what would have been significantly better performance. However, though the Harmoni's cache is smaller, it is clocked at full processor speed, instead of half the processor speed like the original cache. In some processor intensive tasks this turned in better performance for the upgrades.

Overall, from a performance standpoint, both upgrades performed very well on processor intensive chores. Even on some tasks that processor upgrades do not usually do much to improve, such as on-screen graphics, the Harmoni gave a nice little speed boost. If you are considering such an upgrade, you may want to give more consideration to the 500 MHz version over the 600 MHz one. In our testing the 600 MHz was not significantly faster to justify the $100 price premium ... unless you need every scrap of processing muscle you can get.

In our opinion, the best thing about these upgrade cards is not their speedy G3 processor, but the fact that Sonnet has found a way to incorporate FireWire into the upgrades. Finally owners of original iMacs have a way to add a high-speed port to their machines. With this upgrade you can now connect high speed devices, such as the iPod and FireWire drives, to your Mac, and exchange data at a respectable speed. While not at fast as a native FireWire port, the Harmoni port beats any other method of getting data into your iMac. A file that took 257 seconds to transfer through the Ethernet port, took only 10 seconds by way of the Harmoni FireWire port. The Harmoni port turned in about 2/3 the performance of the native FireWire port on a 500 MHz iMac but this could have been due to the faster drive on the 500 MHz machine

Adding a Harmoni upgrade to your iMac is not difficult, but it is complex. For the most part the complexity is due to the fact that Apple engineered these machines in such a way that you nearly have to disassemble the whole machine to gain access to the motherboard. If you have installed RAM into your iMac, especially if you have installed RAM into the bottom slot on the processor daughter card, you know the drill. There are a few more steps required in installing the Harmoni that are not required in a RAM install, namely adding the FireWire circuitry, but really it is no more difficult than that.

If you wouldn't be comfortable installing RAM into your iMac ... then have someone professionally install the upgrade for you. Hopefully this can be done in the same place you purchase the card. Then, if problems crop up, you can have them handled all in one place.

Before you install the card you have to run a software utility that Sonnet provides. Some special proprietary instructions that Apple has installed, reside on the original daughter card (in the ROM chip). Because your iMac will not run without those instructions, they will need to be copied over to the new daughter card you are installing (Apple does not Allow third parties to sell these instructions ... one of the reasons we don't have Mac clones). These instructions will be copied to the hard drive and then transfered into the new upgrade card the first time you boot the machine after the Harmoni installation.

Installation instructions are covered well in the manual that comes with the upgrade card. The illustrations could be a little bigger though, so that the details are clearer.

In raw processing capability, the Harmoni cards turned in what you would expect from cards clocked 2 to 2 1/2 times our test machine, a revision A G4/233 iMac. At processor intensive tasks the Harmoni upgraded iMac showed a 2 to 3 times performance improvement, with the 600MHz card besting the 500 MHz version by about 20%

On tasks that were mixed and that did not rely solely on processing strength, performance improvement was less. However we were pleased to see a 70% improvement in our Excel test and a 40 to 50% improvement in on-screen graphics.

Drive performance did not show much performance improvement, as expected. Indeed in some tests, drive performance decreased. We believe this is largely due to the diminished amount to L2 (backside) cache on the upgrades.

On the stability front, we had severe problems with the first 500 MHz card that Sonnet sent us. They sent us a replacement that performed fine during our performance testing.

We did run across some odd behavior when using the upgraded machine. We encountered several errors when reinstalling System software, and had one odd case where a window was cloned about dozen times. We are unsure that these events were related to the Harmoni upgrades.

The fact that we had upgraded to OS 10.2 and that we had installed addtitionl RAM or that we were running low on hard drive space, may have been factors. A perusal of user reviews of the Harmoni at other sites, we found to be universally positive. Perhaps what we experienced was just some settling in voodoo ...

Still we don't like odd behavior ... makes us cautious. We would urge you, as we usually do, to purchase from a merchant that you trust and that will take the product back should you encounter problems with it. Sonnet stands behind their products with a 3 year warranty, and in the past, when glitches have cropped up, have come through with software fixes. I am sure that they will continue to do so with the Harmoni.

[update 11/1/02: We have now confirmed that the 'cloning' issue is not related to the Sonnet card, and is either a bug in OS X or a problem with the extra memory we had installed. We had the phenomenon replicate itself in other machines running OS 10.2]

Final thoughts

These upgrades are very reasonably priced, especially given the fact that you get FireWire on top of the processor upgrade. At $300 we think the 500 MHz card will be plenty powerful for most people. However if you are doing intensive processing type work the higher clocked card may appeal to you. These upgrades will not give you the equivalent of a stock 500 or 600 MHz iMac, especially in the areas of drive and graphics performance, but they will help, and in raw processing power they come close. There may be some minor glitches with Apple's 10.2 OS upgrade, but if there are we are sure Sonnet will address them. We definitely would like to hear from other Harmoni owners to see what their long term experience has been. If you have a Harmoni upgrade in your iMac drop us a line and let us know how it has been working out for you. We will post your experiences on the site.

Salient facts: A used 500 MHz iMac runs about $600 (you may find a better deal on eBay ... but those sales are not usually backed by a guarantee). If you were hoping for a G4 processor upgrade for your iMac, Sonnet doesn't make one ... yet! However PowerLogix does. A 500 MHz G4 card from them will set you back $370. You won't get the FireWire port and you should check and see if the applications you want to run will benefit from the special performance enhancements of a G4 processor. We hope to be able to evaluate the G4 upgrade from PowerLogix soon.

Product: Harmoni G3/500/500/256K

Company: Sonnet Technologies

MSRP: $300

Hits: Very good at processor intensive tasks, speedy backside cache, FireWire port

Misses: If this upgrade had a full 512K of L2 cache instead of 256K it would be even faster, may have some minor stability problems in OS 10.2 that need to be worked out

Requirements: iMac 233 MHz, 266 MHz, 333 MHz (Rev. A-D). FireWire requires Mac OS 8.6 or later; best compatibility with FireWire devices is achieved with OS 9.1 or later, and OS X Version 10.1 or later (we tested with OS 10.2 and 9.2.2)

Rating: (5 possible)

Product: Harmoni G3/600/600/256K

Company: Sonnet Technologies

MSRP: $400

Hits: Very good at processor intensive tasks, speedy backside cache, FireWire port

Misses: Extra performance may not justify price premium, bigger cache would help, may have some minor stability problems in OS 10.2 that need to be worked out

Requirements: iMac 233 MHz, 266 MHz, 333 MHz (Rev. A-D). FireWire requires Mac OS 8.6 or later; best compatibility with FireWire devices is achieved with OS 9.1 or later, and OS X Version 10.1 or later (we tested with OS 10.2 and 9.2.2)

Rating: (5 possible)

"Real World" Tests

The tests below are from our suite of real world application tests. These tests feature a diverse selection of applications commonly used by the Mac community. The test suite was designed to render an accurate and well rounded picture of a machine's performance. All of the tests below, were timed with a stopwatch. The times were then converted to percentages, relative to the Power iMac G3/233/117/512K, which is set to 100%. For all scores, higher numbers are better. Also included, for comparison purposes, is a stock iMac G3/500/150/512K.

The cache setup for all the options below are as follows:

iMac G3/233: 512K of L2 cache @ 117 MHz (half processor speed)
Harmoni upgrades: 256K of L2 cache @ full processor speed
iMac G3/500: 512K of L2 cache @ 250 MHz (half processor speed)

Desktop Tests

As you can see from the three results above, that where a processor upgrade won't help you out much is in drive activity. The upgraded machine is hurt further by a smaller L2 cache on the Harmoni.

Let 1K Windows Bloom is a simple carbon application that opens and closes 1,000 windows.

Two folders with many items are searched using OS X's new search function. Drive performance puts the Stock G3/500 iMac over the top

Large Photoshop file is scrolled from top to bottom in the Classic layer of OS X

Large Document & Database Type Tests

A Macro (series of complex actions) was run in Microsoft's Excel program, which is part of Office X

Stresses the processing & memory systems of the machine. This test takes place in a large AppleWorks document. This is a raw processing power test in which the size of the L2 Cache plays an important part

Number Crunching & Rendering Tests

The Fractal program is a good test for assessing the fundamental processing potential of each setup. It seems clear that the faster cache on the Harmoni upgrades pushes it ahead of the larger cache on each of the stock machines

A Ripple Effect is applied to an iMovie

Encoding/Decoding Tests

A Sorenson encode compresses a QuickTime movie for streaming on the Web

Preps QuickTime Movie for import into iMovie

The Harmoni upgraded iMac is probably hurt by the slower CD drive of the iMac

Multitasking

MP3 Encode, AppleWorks search & replace and folder copy are all carried out at the same time. The Harmoni upgrades are dragged down by the poor performance of the iMac's drive and their smaller L2 Cache