How do you upgrade the RAM in the "Aluminum" iMac models? How much RAM of what type do these systems support?

The "original/Mid-2007" models and the "Early 2008/Penryn" offically support 4 GB of memory but unofficially support 6 GB, the "Early 2009" models support 8 GB of memory, and the "Late 2009" models support 16 GB of memory. Upgrading the memory in all of these Aluminum iMac models is quick and easy, but different lines use different types of memory.

The Apple Support Site provides a helpful document that covers "Installing or Replacing Memory" in the "two side-by-side Synchronous Dynamic Random-Access Memory (SDRAM) slots in the bottom" of the pre-"Late 2009" Aluminum iMac models and another document that covers the four slots in the "Late 2009" Aluminum iMac models. The upgrade procedure effectively is the same.

The "original/Mid-2007" Aluminum models -- the iMac "Core 2 Duo" 2.0 20-Inch (Al), "Core 2 Duo" 2.4 20-Inch (Al), "Core 2 Duo" 2.4 24-Inch (Al), and "Core 2 Extreme" 2.8 24-Inch (Al) -- use 667 MHz PC2-5300 DDR2 SDRAM, which Apple further specifies must meet all of the following criteria:

• PC2-5300
• Unbuffered
• Nonparity
• 200-pin
• 667 MHz DDR2 SDRAM

The "Early 2008/Penryn" Aluminum models -- the iMac "Core 2 Duo" 2.4 20-Inch (08), 2.66 20-Inch (08), 2.8 24-Inch (08), and 3.06 24-Inch (08) -- use 800 MHz PC2-6400 DDR2 SDRAM, or specifically:

• PC2-6400
• Unbuffered
• Nonparity
• 200-pin
• 800 MHz DDR2 SDRAM

The "Early 2009" Aluminum models -- the iMac "Core 2 Duo" 2.66 20-Inch (Early 2009), 2.66 24-Inch (Early 2009), 2.93 24-Inch (Early 2009), and 3.06 24-Inch (Early 2009) -- and the "Late 2009" Aluminum models -- the iMac "Core 2 Duo" 3.06 21.5-Inch (Late 2009), "Core 2 Duo" 3.06 27-Inch (Late 2009), and "Core i5" 2.66 27-Inch (Late 2009) -- use 1066 MHz PC3-8500 DDR3 SO-DIMMs:

• PC3-8500
• Unbuffered
• Nonparity
• 204-pin
• 1066 MHz DDR3 SDRAM

However, the "Early 2009" models have two RAM slots and support a maximum of 8 GB of RAM whereas the "Late 2009" models have four RAM slots and support 16 GB.

According to Apple, "DIMMs with the following features are not supported" by any of these iMac models:

• Registers or buffers
• PLLs
• Error-correcting code (ECC)
• Parity
• Extended data out (EDO) RAM

The "Installing and Replacing Memory" documents continue with detailed instructions complete with drawings for upgrading the RAM in these iMacs. By following the instructions closely, you should have the RAM upgraded in no time.

Please note that just because RAM meets the minimum listed criteria does not mean that it will necessarily function as intended in a particular Mac. When buying memory, be sure to buy from a quality vendor that has tested their RAM with your Mac to ensure compatibility.

Site sponsor Other World Computing sells memory guaranteed to be compatible with all of the Intel-based iMac models.

Also see: How do you upgrade the RAM in the White iMac "Core Duo" and "Core 2 Duo" models? How much RAM of what type do these systems support?