Mac Daniel's Advice

Why the Slot Loading iMac Is a Good Choice for OS X

Dan Knight - 2004.09.10

Earlier this week I suggested that slot-loading iMacs were a better choice than the earlier tray-loading models if you want to run Mac OS X. Today I will explain why.

The slot-loading iMacs were introduced in October 1999 at speeds of 350 MHz and 400 MHz. Over time, the slot-loaders achieved speeds as high as 700 MHz. Improvements over the tray-loading iMac included a 100 MHz system bus (vs. 66 MHz), a slightly smaller enclosure, and nearly silent operation - there was no cooling fan in the slot-loaders.

They also addressed the two biggest drawbacks of the earlier iMacs. Unlike the tray-loaders, all of the slot-loaders support up to 1 GB of memory. And all of them let you use the whole hard drive (up to 120 GB) for the operating system, applications, and work files.

Slot-Loader Basics

The slot-loading iMacs had a 15" CRT display, moderately slow hard drives (6-7 GB on the low end, and up to 60 GB on later models), and had a variety of media drive options. Some shipped with a CD-ROM, others had DVD-ROM drives, and later models generally included CD-RW. (The slot-loading iMac was never shipped with a Combo drive or SuperDrive, but there are third-party CD-RW, Combo, and SuperDrives available for as little as US$39!)

The hard drive is a standard IDE mechanism, and you can install drives up to 120 GB in size. A fast drive with a large buffer is always nice, and throughput is limited to 33 Mbps - twice as fast as on tray-loading models.

Most slot-loaders have FireWire ports, but the entry-level 350 MHz models left it out, so if you want to use FireWire devices, stick with 400 MHz and faster iMacs.

There were three, four, or five different versions of slot-loading iMacs depending on how you want to count things. Here's a quick overview (also see our Quick Guide to CRT iMacs):

  • Version 1 (Oct. 1999): 350-400 MHz G3, 64-128 MB RAM standard, 6/10/13 GB hard drive standard, 24x CD-ROM or 4x DVD-ROM, v.90 modem. Supports 1 GB RAM. 8 MB video RAM. ATI Rage 128VR video chipset. Requires Mac OS 8.6 or later. Colors: blueberry, strawberry, grape, lime, tangerine.
  • Version 2 (July 2000): 350-500 MHz G3, 64-128 MB RAM standard, 7-30 GB hard drive standard, 24x CD-ROM or 4x DVD-ROM, v.90 modem. Supports 1 GB RAM. 8 MB video RAM. ATI Rage Pro 128 video chipset. Requires Mac OS 9.0.4 or later. Colors: indigo, sage, ruby, graphite, snow.
  • Version 3a (February 2001): 400-500 MHz G3 with backside cache, 64 MB RAM standard, 10-20 GB hard drive standard, 24x CD-ROM or 8x CD-RW, v.90 modem. Supports 1 GB RAM. 8 MB video RAM. ATI Rage Pro 128 video chipset. Requires Mac OS 9.1 or later. Colors: indigo, flower power, blue dalmatian.
  • Version 3b (February 2001): 500-600 MHz G3 with onboard cache, 64-128 MB RAM standard, 20-40 GB hard drive standard, 8x CD-RW, v.90 modem. Supports 1 GB RAM. 16 MB video RAM. ATI Rage Ultra 128 video chipset. Requires Mac OS 9.1 or later. Colors: graphite, flower power, blue dalmatian.
  • Version 4 (February 2001): 500-700 MHz G3, 128-256 MB RAM standard, 20-60 GB hard drive standard, 8x CD-RW, v.90 modem. Supports 1 GB RAM. 16 MB video RAM. ATI Rage Ultra 128 video chipset. Requires Mac OS 9.1 or later. Colors: indigo, graphite, snow.

In brief, the 1999 model has Rage 128VR video, while version 2 and 3a have Rage Pro 128 graphics. Versions 3b and 4 use the Rage Ultra 128 chipset and have 16 MB of video memory, twice as much as the earlier slot-loaders. These last two versions also include an improved G3 CPU with the backside cache built right into the processor.

OS X Suggestions

With enough memory, the slot-loading iMacs can run Mac OS X comfortably. The slower models are no speed demons, but they're functional, and later iMacs with improved video and improved versions of the G3 acquit themselves quite nicely.

The first thing you need to get the most out of OS X is plenty of memory. Although you can run OS X with as little as 128 MB of RAM, you won't be happy doing so. OS X will use your Mac's hard drive to create virtual memory when it runs out of RAM, and that's several orders of magnitude slower than memory chips, so you want real RAM.

I'd call 256 MB an absolute minimum for decent OS X performance, 320-384 MB better, 512-640 MB comfortable, and 768 MB to 1 GB ideal. It's not cheap, but it's the best investment you can make if you want to unleash OS X on any Mac.

The next way to trick out a slot-loading iMac is with a faster hard drive. I'm a big fan of those 80 GB 7200 rpm drives with an 8 MB buffer that are often on sale for around US$80. You may be able to find smaller drives for a bit less, but it's often just a little bit less. You can use drives as large as 120 GB if you need lots of space - those 160 GB and larger drives require a version of the IDE specification not supported on G3 iMacs.

The faster hard drive not only offers faster data access, it makes virtual memory faster as well (the faster IDE bus helps, too).

Avoid used hard drives. Pulls, drives taken out of a new computer so a faster and/or higher capacity drive can be installed are often good deals - when you can find them.

Processor Upgrades

Sometimes a CPU upgrade makes economic sense. If you already have the iMac, have all the RAM you want, and have a good hard drive, expending $299-349 to perk up performance makes sense - and the slower the CPU in your iMac, the more sense it makes.

At this point I know of only two CPU upgrades for slot-loading iMacs:

The iTechDV will offer superior number crunching power, which means faster Photoshop filters, iTunes ripping, and video editing. Unless you do a lot of that, the 900 MHz iForce is probably your best bet. On slower iMacs, it can more than double performance, and even the fastest G3 iMac ever made will be faster with it.

Don't plan on buying an iMac and then adding a CPU upgrade. By the time you do that, you may as well ante up for a nice used 700 MHz to 1 GHz G4 eMac, which will also give you a larger display. But if you already own a slot-loading iMac and want more power, processor upgrades may make sense.

Optical Drives

The biggest drawback of the slot-loaders may be their optical drives. Apple never offered a Combo drive, so you'll have to choose between CD playback only, CD and DVD playback, or CD playback and recording when you pick an iMac. But you're not stuck there. You can pick up a CD-RW/DVD drive for as little as US$45, which means your 400 MHz or faster iMac will be able to play DVDs and burn CDs. Recommended, particularly if you have a CD-ROM or DVD model.

Oddly enough, Combo drives cost less than CD-RW drives!


Upgrading slot-loading iMac so you can use OS X won't cost as much as upgrading a tray-loader. The hard drive is already large enough, although I'd find 6-10 GB very limiting very quickly. And you can add a single 256 MB of 512 MB memory module to boost RAM to a very comfortable amount, which is less costly than buying two modules for a tray-loader.

If you want to replace the CD-ROM, DVD, or CD-RW drive, you have the option of a Combo drive - and even a SuperDrive if you want to burn DVDs. (If that's an interest of yours, get a fast iMac or consider one of the faster CPU upgrades.)

With prices starting at US$209 for an iMac 350 (no FireWire) and US$300 for a 400 MHz iMac with FireWire, the slot-loading iMac is definitely worth the small price premium compared with the tray-loaders. With lower cost add-on optical drives, support for 1 GB of RAM, and no 8 GB partition issue (which the tray-loaders suffer from), it's a great way to go OS X on a budget. LEM

Revised 2004.09.13 to add colors of various models.

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