iMac and eMac Index

Upgrade Guide for Slot-Loading iMacs

Dan Knight - 2003.05.15
Prices updated 2007.08.03

The original iMac was nice, but the slot-loading iMacs are even nicer. Starting with a 100 MHz system bus (up from 66 MHz on the original), the slot-loading iMacs shipped from Apple in speeds ranging from 350 MHz to 700 MHz. They also started out using ATI Rage 128 2x AGP graphics with 8 MB of video memory - a big improvement in the video department, and by the time the G3 iMacs were phased out, they were using ATI Rage Ultra 128 graphics with 16 MB of VRAM. (Video is built into the system board; there is no way to replace it with a better video section.)

The "Kihei" design includes a slot for an AirPort card adapter and runs quietly; there is no cooling fan in this design. Except for the entry-level 350 MHz models (both the blueberry and indigo versions), all slot-loading iMacs included FireWire as a standard feature.

In contrast to the CD-ROM only nature of the originals, slot-loading iMacs shipped with CD-ROM, DVD-ROM, or CD-RW drives - and SuperDrives are available from other vendors. If your iMac doesn't have the drive you want, it should be relatively easy to replace it.

Before investing a lot in upgrades, check our Best G3 iMac Deals to see if you might be better off simply buying a newer iMac that has the features you want.


The slot-loading iMacs typically shipped with 128 MB or 256 MB of memory, and they support up to 1 GB using a pair of 512 MB PC100 SDRAM cards.

That's adequate for the classic Mac OS, but we recommend nothing less than 256 MB for OS X. For really good performance, you should have at least 256 MB under the classic Mac OS and 384-512 MB to get the most out of Mac OS X. With OS X, more is definitely better.

We suggest you visit ramseeker for current pricing on the PC100 SDRAM used in these iMacs. The lowest current RAM prices (Aug. 2007) are 64 MB, $9; 128 MB, $14.99; 256 MB, $20.99; 512 MB, $54.99.

Hard Drive

The hard drives used in these iMacs were chosen because they were inexpensive. They have very limited capacity and often have sluggish performance (Apple often used 4400 rpm drives to keep costs down). At the very least they should be replaced with a larger, more modern 5400 rpm drive. If you can swing it, though, we recommend a 7200 rpm drive with an 8 MB buffer for even better performance, although there may be a chance of overheating with these fanless models. (Note that the iMac doesn't support drives over 128 GB without third-party drivers. See a href= "/2005/how-big-hard-drive-imac-emac-power-mac-powerbook-ibook/">How Big a Hard Drive Can I Put in My iMac, eMac, Power Mac, PowerBook, or iBook? for more details.)

A faster drive is especially helpful if you run OS X, since virtual memory is always enabled. A faster drive can really speed things up.

Media Drives

Slot-loading iMacs may come with a plain old CD-ROM drive, a DVD-ROM drive, or a CD-RW drive. If the drive you have isn't the drive you want, there's a market for new and pulled (removed from new units but no longer factory fresh) drives.

If you want to go beyond what Apple offered, "SuperDrives" (DVD burning) are available.

There are a lot of options for adding an external drive using USB or FireWire. Following are internal drives we've found for the Kihei iMacs.

Replacement CD-ROM drives

Replacement DVD-ROM drives

CD-RW Drives

SuperDrives (CD-RW/DVD-RW)

  • 8x DVD/24x CD, dual-layer DVD burner, 2 MB buffer, MCE Technologies, $149

Processor Upgrades

Once you have enough memory and a fast hard drive, you can really unleash your iMac with a processor upgrade. Because Apple used two different versions of the G3 during the life of the tray-loading iMac, there are two different types of processor modules. At present CPU upgrades are only available for iMacs with the standard PowerPC 750, which includes all models slower than 500 MHz and some 500 MHz iMacs.

Some 500 MHz models, especially those intended for North American use, and all faster iMacs use the PowerPC 750CXe and cannot be upgraded at present.

CPU upgrades

  • iForce SL G3/900, uses PowerPC 750FX, PowerLogix, disc.
  • iTechDV G4/500, 1 MB L2 cache, TechnoWarehouse, disc.
  • FastMac G4/550, 1 MB L2 cache, $199.95 (add $29.95 for advance exchange), logic board swap, supports 350-450 MHz and some 500 MHz models
  • XLR8 550 MAChSpeed G4, 1 MB L2 cache, $199 + $50-120 for shipping, logic board swap, factory installed, supports 350-450 MHz models, disc.

Under the classic Mac OS, there is not much benefit from the G4 unless you're working with video, ripping sound tracks, or working with complex Photoshop images.

On the other hand, OS X really benefits from the AltiVec velocity engine in the G4 processor. Not only will video, graphics, and MP3 ripping benefit, so will the Aqua interface.

Other Improvements

Most users find the Apple Pro Mouse and Pro Keyboard excellent. There are lots of options in USB mice and keyboards if you disagree; we suggest you go to your nearest Apple retailer and take a look at the wide array of third-party mice and keyboards available from Logitech and other companies if you aren't impressed with Apple's offerings. (If you like the idea of a wireless setup, we're huge fans of the now-discontinued Logitech Cordless Elite Duo.)

Go to the iMac index.

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