Sonnet CPU Upgrade Kits for Mac

Some time back we looked at a PowerLogix processor upgrade for a Macintosh G3 computer. This week we examine a Sonnet upgrade package for an early iMac.

There are many reasons why one replaces a computer. These days physical reliability usually isn't one of them. Speed has to be one of the top reasons. Somehow computers appear to just slow down with time. I know it isn't merely a matter of perception either. Where an application used to snap open, it now trundles warily. Part of the problem is that application upgrades invariably bundle additional features into the program, all of which tax a CPU to a slow death. Ultimately, hardware replacement is the only answer. Pity, especially if the unit is otherwise rock-stable.

Enter the after-market refitters. In the Mac realm, there is a surprisingly large number of non-Apple hardware companies that cater directly to the Mac upgrade market. A CPU upgrade can give a computer a new lease on life, keeping in mind of course that a lease always has a termination date. But getting inside a Mac box has been notoriously difficult over the years. At least two companies have done rather well in this area. These are PowerLogix and Sonnet, which specialize in processor and related upgrades for Macs. I can now claim successful experience with CPU upgrades from both companies.

The HARMONi G3 processor upgrade kit is made for Rev. A to Rev. D (tray-load) iMacs. Installation is basically a two-step process. First, you run the installer from the included CD. Then you install the hardware and power up the computer. Setup is automatic. As always, read your documentation from cover to cover thoroughly before opening anything.

After having had the fairly hair-raising experience of breaking open a slot-load iMac, I found the tray-load case to be a tinkerer's dream by comparison. The Sonnet documentation includes plenty of pictures and arrows of how things go together. It was straightforward enough to pop off the iMac's bottom plate and remove the modular chassis. You'd also do this same procedure if you were to replace the hard drive.

This iMac's processor is soldered onto a CPU daughter card, which is fairly easily removed with the included tool after popping off the aluminum shield plate and heat sink. Be careful and patient here. Coax the board out. No forcing is required. Take all the static shield protections you possibly can. In particular, always touch the chassis before any component. Also, the instructions suggest prying off cable harness connectors with a screwdriver. Don't do that! Merely apply gentle but firm finger pressure to coax each one out, just as you will the CPU board.

You'll want to remove the additional RAM, if any. It mounts on the top-side of the CPU board, and flips up once you release the two side clips. Again, fingers only, and watch that static. Lay the RAM module aside safely.

I suggest practicing the CPU board installation using your original one before opening the Sonnet static-protect package. Notice the two front locating tabs. Insert these, then feel the two board connectors mate underneath before you press down on them firmly. You need to feel them seat home. Do this a couple or three times until it feels right to you, because ultimately you're blind when seating this board. The new board looks very similar to the original, and utilizes the same heat sink. Oddly enough, there was no heat sink grease in the Sonnet kit. I believe there should be. You can purchase a small tube of heat sink grease from Radio Shack, among other places. Now that you've read this article, you can buy this ahead of time. As you apply it, remember that less is more.

Once you have popped out your original daughter board, you'll transfer the lower RAM module from it to the new Sonnet board. Leave the upper RAM module aside for now. Take all static precautions. As you install the new daughter board, you'll appreciate having rehearsed the procedure. Be confident that you have seated the pair of inter-board connectors. You have to press down with your fingers on the circuit board itself directly above those connectors, so once again be sure to touch the chassis first. If you power up later and fail to get the boot time Apple chord, odds are pretty good that this board isn't seated.

The Sonnet kit includes a clever FireWire port. You may or may not choose to use it. Unless you have a clear FireWire application, I'd somewhat recommend foregoing this step. Then, the upgrade simply becomes a matter of swapping daughter cards and RAM modules. If you choose to add this port, then be quite careful with cable connectors and wire routing. Your chassis may not look identical to the one in the pictures. You will want to run the power tap for the FireWire port underneath your existing cable harnesses. With a slight bit of cleverness, you can get this laid out neatly and relaxed as well.

As you prepare to reassemble and tighten down screws, lay aside everything you learned at diesel mechanics school. These are lightweight screws into sheet aluminum, and easily stripped. Barely firm is plenty tight enough.

Slipping the reassembled chassis back into the iMac case is a little tricky. Watch for plastic protrusions. There are two plastic locators along the slide rail, which will require a little coaxing. Once they clear, however, watch your fingers.

The first time you power up your newly-upgraded Mac, expect to hear the Apple chord, followed by a series of odd beeps. Just let it go and do its thing. Presently it will reboot automatically. The last step in the process should be a window that announces a successful processor upgrade.

If you are running anything earlier than Mac OS 9.2.x, then be sure to install the FireWire drivers now. The procedure is clearly laid out in the Quick Start manual.

My particular test iMac runs Mac OS. While it booted fine afterwards, and immediately demonstrated snappy performance, presently the mouse and subsequently the keyboard locked up. I immediately suspected old USB Overdrive drivers, which indeed turned out to be the culprits. I'll wager that any timing-sensitive drivers will require upgrades if they're very old. To remove these, reboot and hold down the Shift key after you hear the Apple chord. This will boot Mac OS with extensions off. Now open the Extensions Manager from the Apple Menu, Control Panels menu and uncheck the two USB Overdrive extensions (or any other extensions you may suspect). Close and restart.

Suppose you're contemplating such an upgrade as this, and further suppose that a kit is available for your machine. Should you do it? Maybe. If you find the machine otherwise eminently useful but for its speed, then an upgrade is probably indicated. If it's just a whim, or if the machine is flakey in any way, then leave it alone. The risk of permanently damaging it is small, but still non-zero. If indeed you do break the machine hopelessly, you'll need another Mac into which to pop your iMac's hard drive, so that you might recover your data. As for operating system, all of these CPU upgrades are approved for both Mac OS and Mac OS X, so that's not an issue. Atypical hardware or software, particularly timing-sensitive applications such as digital audio stuff, could turn out to be troublesome, though. It's your call.

Sonnet offers a satisfaction guarantee on its products. In the unlikely event that the new CPU just won't play well with your setup, then you can return the kit within 14 days. This policy isn't apparent on the Sonnet website, so be sure to confirm it at time of purchase. You may want to restore your previous BIOS firmware. Unfortunately I cannot tell you at this time whether it's possible to revert back to the earlier code. Fortunately your iMac and its original CPU should run just fine with the Sonnet firmware anyway, as is the case with PowerLogix upgrades.

Speaking of hard drives, backing up your iMac or cloning your hard drive for the sake of a hard drive upgrade might be best facilitated with an external FireWire drive, begged, borrowed, or stolen temporarily. Without some clever juggling, an iMac can handle only one internal hard drive at a time. If I were doing this, I'd sweet-talk my Mac dealer into loaning me an external drive for the job. Now that your iMac has a FireWire port, this is an option.

Hardware upgrades are always a good way to extend the life of your current investments. Additional RAM is the single best upgrade you can give any computer, but a CPU upgrade comes a close second. The Sonnet HARMONi G3 upgrade brings the performance of a Rev. x iMac near to par with the most recent G3-based iMacs. For the money, that's a pretty good deal. Ciao.