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August 5


Upgrading popular iMac involves major computer surgery

Many readers have written in asking about upgrading iMacs. With over five million sold, Apple’s iMac may be the most popular personal computer around. A market of over five million users means that there are plenty of companies willing to help with upgrades.

The iMac’s unique enclosure does make it a challenge to fit parts into a small space, but manufacturers have come up with plenty of innovative solutions. Be warned now: digging around in your iMac’s guts will void your warranty, if you are uncomfortable at all with this process you should contact a professional. Since the iMac has the monitor integrated into the enclosure, you should also know that the monitor CRT tube assembly retains dangerous voltages, be careful.

Now that we are finished with the disclaimers, here is the meat. There are three main upgrades that iMac owners may want to consider: RAM, hard drive, and processor. You will need to know what version iMac you have. They are broken down into two major categories: the early ones up to 333mhz, and the newer ones running at 350mhz of higher.

Older iMacs (233-333mhz) support a maximum of 256MB of RAM in two slots. This would be two 128MB DIMMs. Be sure that you have low profile DIMMs, as the space is quite constrained. To add more RAM the entire motherboard needs to be removed through the bottom of the computer. It can be tricky. For detailed instructions go to

Newer iMacs support up to one gigabyte of RAM in two slots (two 512MB DIMMs). On these machines there is a door on the lower back of the computer that can easily be opened with a coin. Always use a grounding strap when replacing RAM. A slight static electricity discharge can fry sensitive RAM chips.

The original 233mhz Bondi Blue iMac had only two megabytes of VRAM (Video RAM). This is special RAM used for displaying images on the screen. This too can be upgraded to a maximum of 6MB. This is a good, inexpensive upgrade if you are already adding more RAM. More VRAM will allow for more colors and higher resolution on your monitor.

When buying RAM, make sure that the vendor specifies that it is for an iMac. You will need to let the vendor know the type of iMac that you have. Vendors like RamJet ( have lifetime warranties against inherent defects in their RAM. They also verify that their products are compatible with all of Apple’s recent firmware updates.

Replacing the internal hard drive of your iMac is even trickier. The drive is a standard IDE (integrated drive electronics) drive. Again, the iMac’s motherboard and CD-ROM drive must be removed to access the hard drive. Check for the steps in this procedure. It is much simpler to purchase an external Firewire drive and connect it to your iMac’s Firewire port.

There are several processor upgrades for iMacs. They typically replace the existing processor daughtercard. At the risk of being redundant, the motherboard does again need to be removed. Be sure that the upgrade card you purchase is specifically for an iMac. Reputable manufacturers will also note with what speed of iMac their upgrade is compatible.

At this point you may realize that upgrading your iMac requires a lot of major computer surgery. It does, but as long as you are patient, follow the directions and take the recommended precautions it should go smoothly. But most of these procedures are not for the faint-of-heart. If you have any doubts, contact your Apple Authorized Service Representative.

Paul Vaughn is a freelance writer, graphic artist and web designer. Have a Mac-related question?

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