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Upgrading an Old iMac to Mac OS X

Just before Christmas, with a little help from my friends in the TidBITS community, I upgraded two old iMacs to Mac OS X. When Jaguar was first released, I purchased the Mac OS X Family Pack (5 installations) with these machines in mind, but I had put off upgrading the iMacs for a couple of reasons. Somewhere I had picked up the idea that it is possible to kill the iMac if you don’t upgrade the iMac’s firmware properly before installing Mac OS X. I was also afraid that Panther would run so slowly on a G3-based iMac that I would regret having installed it. Luckily, it turns out that my fears were entirely unfounded. Both upgraded machines run just fine. As Geoff Duncan pointed out in TidBITS a while back, while the firmware upgrade is critically important, it’s not hard to do it right. Anyway, I am here to report that you don’t have to be an expert to upgrade an old iMac yourself, and when you’re done, your iMac will have a new lease on life.


The two iMacs I upgraded were both 2001-vintage slot-loading models: a 350 MHz model with 192 MB of RAM (the original 64 MB plus a 128 MB upgrade DIMM), and a 400 MHz model with only the original 64 MB of RAM. These two machines presented somewhat different problems. The first machine, running Mac OS 9.0, was sitting in my office gathering dust; its hard disk contained nothing that needed to be saved. With this one, I wanted to run Mac OS X simply so it could run the Mac OS X applications I rely on everywhere else. The other machine, running Mac OS 9.1, belongs to my mother, and I wanted to upgrade it partly so she could use modern applications like iPhoto and Mail, and so I could more easily support her when she had problems. This machine’s hard disk stored all her files (email, photos, some word processing) and one important Mac OS 9-only application, Stitch Painter 2. I was pleased to learn from a rep for Cochenille, Stitch Painter’s developer, that a Mac OS X-native version is in the works, but because it’s not expected for many months, I decided that keeping Classic on this machine would be necessary. And although I didn’t download it until the end of the process, before doing anything, I also confirmed that a Mac OS X driver exists for her HP combination fax-copier-printer. (Drivers for this printer do not appear to be included with the Panther installation.)


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In what follows, I have stuck fairly close to what I did with my own two machines. Before you set out to upgrade your own iMac, make sure you spot the differences between your machine and those I upgraded, and do a bit of research yourself to make sure you aren’t missing something important to your own situation.

What I Needed — Apple recommends that machines running Mac OS X have at least 128 MB of RAM. I knew that more would be better, so I ordered 512 MB DIMMs from my favorite memory vendor, Crucial Technology ($103 each on 04-Jan-05), one for each iMac. These iMacs have two memory slots, so I knew I’d be able to use both the new 512 MB module and an old module, and end up with a decent amount of RAM. [Editor’s note: Ironically, I was also upgrading an old iMac to Mac OS X over Christmas, but my grandparents’ iMac was a tray-loading 333 MHz model (Rev. D), and apparently only some models of that iMac can see a 256 MB DIMM in the top slot, whereas others are limited to a 128 MB DIMM. I lucked out, so my grandparents’ iMac ended up with 288 MB of RAM, which turned out to be plenty for their Mac OS X needs. -Adam]



I also had to figure out what version of the iMac firmware my machines needed. At first, I found the article on Apple’s Web site a bit confusing, but with the help of Apple’s System Profiler, a Mac OS 9 utility present on both of my machines, I was able to determine current firmware version and also the processor speed of each machine. The processor speed helped me find the right row in the Apple chart for my machines. Both of my iMacs needed to be upgraded to firmware version 4.1.9. Your iMac may need a different firmware version, or its firmware may already be up to date, so be sure to research your own situation carefully.

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I discovered that the 4.1.9 firmware updater wouldn’t work on my iMac because it was running Mac OS 9.0 and the firmware updater requires 9.1 or 9.2. Lucky for me, I’m a packrat and had the box for Mac OS 9.1 handy. Even if I couldn’t find the 9.1 CD, I could have downloaded the 71 MB Mac OS 9.1 upgrade from Apple.

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The last thing required for the upgrade process was time. It took several hours to perform each of these upgrades. My iMac had to be upgraded twice (Mac OS 9.0 to 9.1, then 9.1 to Mac OS X). My mom’s iMac didn’t need the 9.1 installation, but I did spend some time backing up her files and cleaning out some other stuff.

Step by Step — Once I had collected all the ingredients, I proceeded with the recipe as follows. Note that the sequence of the steps here is important.

  1. BACKUP DATA AND RECORD SETTINGS. One of these machines had no important files on it, and I was content to lose everything on the hard disk as a result of the Mac OS X installation. But the other machine (my mother’s) did have valuable files, so backing up was the first step. I enabled file sharing on this iMac, then copied its files over the LAN to my PowerBook G4. (As it turned out, no files were lost during the upgrade process on this machine, but I don’t perform even simple updates without backing up. The last thing I wanted to do was explain to my mom that I’d lost all her knitting patterns!)

  2. SAVE IMPORTANT PASSWORDS AND SETTINGS. I talked to my mother to make sure she had a record of information that would be needed after the upgrade: account names and passwords for her Internet access provider and various Web sites she used to do banking, buy groceries online, etc.

  3. UPGRADE TO MAC OS 9.1. As I mentioned above, I had to do this on my iMac because the firmware update requires 9.1. My mom’s iMac was already running 9.1, so I didn’t have to do this on her machine.

  4. UPDATE THE FIRMWARE. I downloaded the firmware update from Apple, read the instructions, and followed them carefully. The only tricky part here was that the firmware updater asked me to perform a maneuver I’d never performed before: holding down the programmer’s button on the side of the iMac while powering the machine back on and then waiting for a long alert sound (more of a toot than a beep) before letting go. I recommend that you print the instructions out and do a dry run of the process to make sure you understand what buttons you are supposed to press and when.

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  5. INSTALL MORE RAM. This involved opening the back of the iMac, removing the smaller memory module completely, moving the larger module into slot #2, and placing the new module into slot #1. (If you place the iMac face down on a clean cloth, the #1 slot will be the upper slot as you peer into the upgrade area.) When I finished the upgrades, my iMac had 640 MB of RAM (512 plus 128) and my mom’s had 576 (512 plus 64). I wish my hands were a bit smaller, because the iMac doesn’t give you much room to move. And I was confused for a few minutes during one of the installations, because I was trying to insert the new module upside down. But otherwise, upgrading memory in an iMac is straightforward and the only "tool" required is a coin to unlock the iMac’s upgrade panel. Keys here: Wash your hands first, work in a well-lighted place, be patient, discharge static from your body, don’t touch anything inside the iMac except the catches on the memory modules and the plastic edges of the modules themselves, and remember which side is up when you put a new module into the slot. In short, follow the instructions at the first link below or as provided with the memory module. [Editors note: It appears that installing RAM in an older iMac is more involved, but I too found it straightforward after following Apple’s instructions at the second link below. -Adam]

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  6. INSTALL MAC OS X 10.3. On one machine I did an "Erase and Install". On the other machine, I installed Mac OS X over Mac OS 9 and the existing files. Because neither iMac has a large hard disk, I performed a custom install in both cases and told the installer not to install unneeded language modules. For a bit of good general advice on performing Mac OS X upgrades and updates, I recommend Joe Kissell’s "Take Control of Upgrading to Panther" ebook.

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  7. UPDATE CLASSIC TO MAC OS 9.2.1. I didn’t install Classic on my iMac at all, but I did keep Mac OS 9 on my mom’s machine, which was running 9.1 originally. The 9.2.1 upgrade provides better compatibility between Classic and Mac OS X. The CD for this installation was in the box for one of the earlier versions of Mac OS X; you can download it from Apple; or you can use the Software Update control panel in Mac OS 9 to download and install it.

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  8. 8. UPDATE MAC OS X TO 10.3.7. I ran Software Update (from the Apple menu) and installed all the appropriate updates to take each machine from the original 10.3 to 10.3.7. Software Update also updated many of the Apple applications such as Safari, Mail, and iPhoto. I had to do this a couple times; apparently Software Update can’t perform all the updates at once. For some advice on using Software Update, take a look at a recent article on John Gruber’s Daring Fireball site.

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  9. RECONFIGURE. I provided the Mac OS X Network preference pane with the info needed by each iMac to connect to the Internet.

  10. 10. UPDATE DRIVERS, APPLICATION SOFTWARE, TRANSFER DATA. On my mom’s iMac, I downloaded and installed the Mac OS X driver for her all-in-one HP printer. I moved her old data into her user’s Documents folder in Mac OS X, and I imported all her old photos into iPhoto. I was also able to import her old Internet Explorer bookmarks into Safari. When it was all done, I tested both machines online and also ran a few applications such as iPhoto and Safari.

Merry Christmas — Everything works great! It was almost like getting a new iMac for Christmas. I had been toying with the idea of buying processor upgrades or larger hard disks for these machines, but now I don’t think I’ll bother. (If you want to go beyond simply upgrading the operating system, see the following article from Macworld online, which explains how to upgrade both memory and the hard disk on an old iMac.) I haven’t tried editing video on either machine and don’t plan to, but for email, the Web, iPhoto, and the few other applications I intended to run on these machines, everything seems very good. I’m mainly sorry I waited so long to upgrade these elderly iMacs to Mac OS X.


[William Porter is a former classics professor who, in 1998, gave up academic tenure to pursue "other interests," including developing database applications. An Associate Member of the FileMaker Solutions Alliance, Will is currently working on a book about FileMaker Pro 7 for No Starch Press.]

PayBITS: Do you have an aging iMac in need of updating? If William’s

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