The flat-panel iMac’s friendly form masks a computer that can be devilishly difficult—but not impossible—to upgrade. Although you risk damaging your iMac if you perform the following procedures incorrectly, taking those risks can bring rich rewards, such as maximizing your iMac’s internal RAM without having to pay Apple a $200 premium for additional RAM (and installation). In addition, you don’t have to pay a technician to upgrade your iMac’s hard drive (and your iMac will be up and running far more quickly).
Upgrading the internal RAM and hard drive is a complicated process. These upgrades will void your warranty, and if you perform them, you’ll leave clear evidence that you’ve opened your iMac. If you’re not comfortable rummaging around inside a computer, don’t upgrade your iMac beyond installing an AirPort card and additional RAM in the user-upgradable area of the iMac.
Now that you’ve been suitably warned, turn off your iMac and take the following steps to upgrade its RAM and hard drive.
What You’ll Need:
#0 Phillips screwdriver
#15 Torx screwdriver
#10 Torx screwdriver
Project Difficulty: Hard
Step 1: Make the Mac Comfy
Retrieve the box your iMac came in and remove the Styrofoam piece that secured the iMac’s base and screen. Place the rounded portion of the Styrofoam on a work surface with the open slot facing you. Detach all the iMac’s cables except the power cable. While supporting the iMac’s neck and base, lay the iMac on its back so that the arm and screen lay atop the Styrofoam and the Apple logo on the front of the iMac faces right. You may want to place a towel beneath the iMac base to protect your work surface and the base.
If you’ve disposed of the original packaging, construct a protective cradle for the iMac’s display out of stacks of books and a towel.
Step 2: Access the User-Upgradable Components
Using a #0 Phillips screwdriver, loosen the four screws at the bottom of the user-access plate. These screws remain attached to the plate, so once they’re loose, pull on two of them to remove it. Set it aside.
Beneath the cover is the AirPort card slot (A) and one user-upgradable RAM slot (B) . Before proceeding, touch the inner metal plate to discharge any static electricity you may harbor; then unplug the iMac’s power cord.
(If you intend to upgrade the iMac’s internal RAM and hard drive, don’t upgrade the RAM and AirPort card yet. The RAM and AirPort slots should be empty when you access the interior of your Mac. If they’re occupied, remove the RAM and AirPort card, and then replace them when you’ve completed the internal upgrades.)
The user-upgradable RAM slot accommodates a 128MB, 256MB, or 512MB PC133 SDRAM 144-pin SO-DIMM. To upgrade the RAM, insert a compatible RAM module at a 45-degree angle and press it into place. To add an AirPort card, slide the card in so that the AirPort label faces down, and attach the AirPort antenna.
These iMacs can hold as much as 1GB of RAM, but the default amount of RAM in new iMacs is only 256MB. Because you can’t purchase 768MB of RAM on a single module, it’s impossible to upgrade the iMac’s RAM to its full capacity via the user-upgradable RAM slot unless you have 512MB of RAM in the internal RAM slot. The following steps will show you how to upgrade an iMac’s internal RAM.
Step 3: Remove the Bottom Housing
Using a #15 Torx screwdriver, remove the four Torx screws from the bottom of the metal housing (C) .
Place your fingernails in the plastic seam that runs around the bottom of the iMac’s base, and gently pull down so that the bottom housing opens toward your work surface (D) . Put a phone book underneath the housing to support the edge closest to you (you could damage the cabling inside the iMac if you force the bottom housing to lay flat).
To detach the bottom housing from the upper base, you’ll have to disconnect six cables: the rectangular power connector (E) , the hard-drive and optical-drive data connector F, the AC-line filter connector (G) , the AirPort-antenna connector (H) , the video connector and its cover (I) , and, once you remove the Torx-10 screw, the grounding cable (J) . Pay attention to how these cables are arranged so you can put them back properly.
Step 4: Upgrade the Interior RAM
The iMac’s internal RAM slot requires a PC133 SDRAM 168-pin SO-DIMM. To upgrade the RAM in this slot, pull apart the ejector tabs on the side of the RAM currently in the slot and lift out the RAM. Line up the notch in the new RAM with the key in the RAM slot. Insert the new RAM in the slot, and press down until the ejector tabs snap into place.
Step 5: Remove the Drive Carrier Assembly
In the upper portion of the iMac’s base is a large silver box. This is the drive carrier assembly—a bracket that holds both the optical drive and hard drive in place. Before removing it, rotate the iMac’s base so the Apple logo faces up.
Remove the two Torx-10 screws that hold the EMI shield in place (K) . A strip of copper tape attaches the EMI shield to the optical drive (L) . Peel this tape away from the optical drive, set it aside, and then gently pull off the EMI shield.
Remove the drive carrier assembly’s four Torx-10 screws (M) . Grip the assembly in both hands and firmly pull up and out. There are power cables attached to the assembly, so don’t pull so hard that you risk stressing these cables. Once the assembly is clear of the base, turn it to the right.
A white cable clip is attached to the top of the carrier assembly just above the optical drive. The video and AirPort antenna cables are routed through the clip. Press down on the cable clip to open it, and pull the cables away from the clip so the carrier assembly is no longer tethered to the iMac.
Detach the power cable that’s connected to the hard drive (N) . Pull gently but firmly on the connector , not the cable. (Pulling on the cable may damage it.)
Step 6: Remove the Hard Drive
The hard drive is covered by a white wrapper that’s sticky on one side. You must peel it away to access the screws that attach the hard drive to the carrier assembly. Carefully remove the wrapper (O) , and stick a couple of its corners to the outside of the iMac’s base to keep it from sticking to itself.
Detach the data cable from the hard drive and remove the four Torx-10 screws—two on each side of the assembly—that hold the hard drive in place P. Slip the drive out of the assembly and replace it (15-inch flat-panel iMacs use Ultra ATA/66 7,200-rpm hard drives by default).
Step 7: Replace the Hard Drive and Reassemble the Carrier Assembly
Reassembling the iMac mostly requires working backward through the steps you followed to disassemble the computer. After screwing the new drive into the bracket, attach its data cable. Replace the white wrapper, carefully smoothing it down as you go.
Thread the video and AirPort antenna cables through the cable clip and reattach the power connector to the hard drive. Push the carrier assembly back into place. Be sure the data cable that attaches to the iMac’s motherboard is not trapped beneath the assembly.
Replace the four carrier-assembly screws, put the EMI shield into position, and press the copper tape onto the optical drive. Replace the two EMI shield screws.
Step 8: Apply Thermal Paste
A thermal pipe inside the iMac draws heat away from the processor and vents it through the base of the computer (Q) . The outlet for this thermal pipe sits flush against a mating surface (where the two parts meet) attached to the upper part of the iMac’s base (R) . Between the thermal pipe and mating surface is a thin coat of silicon paste (known as thermal paste or heat-sink compound). This paste—available at electronics shops for around $5 a tube—helps eliminate air gaps between the surfaces, so heat goes out the pipe rather than into the iMac.
When you separate the bottom housing from the base of the iMac, you break the thermal seal. You must restore it with a fresh coat of thermal paste when you reassemble the iMac.
To do so, first scrape off the old thermal paste from both surfaces with the edge of a credit card. Don’t use an abrasive material, since it may score the surfaces and create gaps that prevent the connection from sealing properly. Also avoid liquid cleaners—they could damage the iMac’s internal parts. When the surfaces are clean, smear a thin layer of thermal paste on the mating surface and spread it evenly (S) . Remove any paste that gets in the vent hole.
Step 9: Reattach the Bottom Housing
With the iMac thoroughly pasted, reattach the grounding cable, the video connector and its cover, the AirPort-antenna connector, the AC-line filter connector, the hard-drive and optical-drive data connector, and the rectangular power connector. Then replace the screw that holds the grounding cable in place. Important: Tuck the cables inside the iMac’s base—if you pinch the power cable between a screw post and the edge of the housing, you could cause a short that will destroy your iMac! Push the bottom housing into place and screw in the four Torx-15 screws. To ensure a tight seal, tighten these four screws so they’re firmly in place (but not so tight that you can never loosen them).
Install the RAM module and AirPort card that sit beneath the user-access plate, attach the Air-Port antenna, and then screw the plate back into place.
Editor’s Note: This article was written with assistance from