Upgrading a G3 400 iMac OS 9.1 to OS x?

Make sure, first, that you run ALL the updates for Mac OS 9 and the iMac -- ESPECIALLY THE FIRMWARE UPDATE. Without the Firmware update, you will lose video when installing Mac OS X -- even booting to the CD will turn your iMac into a doorstop. There is a way to recover from this, but many, many hoops to jump through. Ask me how I know.

First, open a web browser (Internet Exploder or Netscape are probably already on the machine) and download the Mac OS 9.2.1 updater HERE (you might need to "click to agree" a couple times). Open the installer, run it, and restart.

Now open the browser again and download the Mac OS 9.2.2 updater HERE (again, you might need to click to agree) Again, open the installer, run it, and restart.

The one you particularly need to watch for is the Firmware Update: go HERE and download it. Open the installer, run it, and shut down.

Now the tricky part. Look at the I/O bezel on the left panel of the iMac. Do you see the two buttons, one next to the other? The one that's raised is the Reset button (You can, in an emergency, push this one to restart your Mac if it's completely frozen and won't respond to anything else. Use with caution). The one that's inset is the Programmer's button. You'll need to push and hold this with a straightened paper clip or similar tool to update the Firmware.

Using your straightened paper clip, push and hold the Programmer's button and don't let go. Push once on the Power button and let go. The machine should respond with a long high-pitched tone. Let up on the Programmer's button and the machine will give a progress bar, then restart itself when the update is complete.

At this point, you can use the automated Software Update control panel to check for other updates. Go to Apple Menu > Control Panels > Software Update. Click "Update Now." The machine will download and install some updates and ask you to restart. After the restart, repeat the Software Update / Restart sequence until it tells you that your software is up to date.

Congratulations -- you're now ready to install Mac OS X. Provided, of course, that you have the RAM, hard drive space, and proper configuration to install the version you'd like. I've used 10.4.11 quite nicely on a G3/400 (Graphite), but it's a lot happier with 512MB RAM and an 80GB hard drive. Good luck!

Thanks! Very precise upgrading advice! Now about the OSX version. Is there one better than the other that will handle all my OS9 software? I agree I need more RAM, What type is it and where is a good place to get it? And I have an external 500gb hard drive. Is that good enough or should I install a different internal drive. What internal drive is best?

That's why we're here.

All the versions that this iMac can handle (10.0, 10.1, 10.2, 10.3, 10.4) will handle your OS 9 apps just fine in Classic mode. Or you can use the Startup Disk preference pane to boot back into OS 9 for that occasional app that won't behave in Classic mode.

You need PC133 SDRAM (full-sized, desktop-style sticks). This machine can take up to a pair of 256MB sticks (some have even had luck with a pair of 512MB sticks). Sticks of these sizes *must* be low-density sticks, with chips on *both* sides of the stick. Otherwise, your iMac will not like it -- it might see just half the stick, or not see it at all, or refuse to boot. Make sure you get low-density sticks if you get 256 or 512MB RAM.

Where to get it? How about in the buy/sell/trade section right here in AppleFritter? Lots of good folks out here that know what you need for the machine you've got. Start a "want to buy" thread and see what happens.

That depends on the type of external drive and what you intend to use it for. If you're looking to install Mac OS X on the external drive and boot from that, you'll want a FireWire drive, preferably a LaCie. This Mac probably won't boot to USB, and even if it did, it would be painfully slow.

Any major brand should be fine -- I prefer a Seagate or a Hitachi myself, but others have equally strong and valid opinions: your mileage may vary.

You'll want a 3.5" IDE (or ATA or PATA -- all the same thing -- but not SATA or SCSI) hard drive, at least 40GB and not more that 128GB. This logic board can't see over 128GB on a single internal drive, so a larger drive will result in wasted space. Also, Mac OS 9 can't deal with drives larger than 200GB or so anyway, so booting to 9 or running Classic won't happen on a large drive either.

Again, good luck!

This iMac still has the < 8GB boot partition limit, doesn't it? (okmatthew; some of the older Macs required OS X be installed on a boot partition smaller than 8 GB. You could still use the full 500 GB of your drive, but you may need to split it into several partitions)

If you want to stick with a Mac, you might consider the iMacs are infamous for dying analog boards resulting in no video. Before investing your limited funds in the iMac, could I recommend you take a look around ebay at some of the lower-end G4 desktops. You might be able to find one with OS X pre-installed.

Actually, it was only the tray-loaders (233, 266, 333 MHz) that had the 8GB boot partition limit. The slot-loaders (350, 400, 500, 600, 700 MHz) did not. And the logic boards in all G3-based iMacs (and the very first G4 iMacs) would see up to, but not beyond, 128GB. There are third-party hacks to make the machine see a partition in the "wasted space," but I haven't tried them to see how well they work.

I believe the 8 gb limit is only on the tray load imacs. The 400 mhz imacs will run os X pretty decently (os X version 10.3 and 9.2.2 in classic worked best for me)
I have one with between 384 and 512 of ram (can't remember off the top of my head) but its been running for a few years now just fine, it can't really handle some more media intensive websites or multiple tabs in a browser, but otherwise it can do most tasks. I also upgraded it from the original ~13gb HD to an 80 gb model which was very cheap, it wasn't too bad of a job to get inside iirc.

Thanks! To swap machines... Well that is the final question. Is it worth the trouble to upgrade this imac? By the time I get a new drive and RAM and OS and HEADACHES from doing all this, maybe I should just get a G4? I've seen em ina pawn shop for a couple hundred. If it would get to the Internet reliably I'd almost give it to my daughter but it doesn't work as good as my PC and I don't want to give her a headache. Any Opinions out there?

I've seen fairly complete dual 500MHz G4 towers for $50 at the local used computer store, not reconditioned and maybe be missing a HDD or RAM or something. I wouldn't spend a couple hundred on one unless it was very complete and known to be in good working order. For the price of a G4 you can pick up a P4 desktop with much better specs. I hate telling people that because I like Mac OS, but the Mac vs PC value equation really stretches quite far on used G4 systems unless you look for a good bargain.