How do the "Late 2009" Aluminum iMac models compare to the "Early 2009" models that preceded them?

Please note that all Macs mentioned in this Q&A have been discontinued. The "Late 2009" iMac models were replaced by the "Mid-2010" line on July 27, 2010.

The "Late 2009" iMac 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) -- look quite similar to the "Early 2009" models -- the 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).

One easily could be forgiven for mistaking the two lines. However, the most noticeable difference is that the "Late 2009" models -- with 21.5" and 27" displays -- have an "edge-to-edge" glass design and "seamless all aluminum enclosures".

Photo Credit: Apple, Inc. (Late 2009 -- 21.5" - Left, 27" - Right)

The "Early 2009" models -- with 20" and 24" displays -- on the other hand, have a modest aluminum border around the display (note the difference between the lower corners around the display in the above and below photos) as well as a black plastic back.

Photo Credit: Apple, Inc. (Early 2009 -- 24" - Left, 20" - Right)

Both the "Early 2009" and "Late 2009" models have the entire computer tucked discreetly behind a glossy flat-panel display. However, the LCD displays used in the "Late 2009" models are LED-backlit, higher-quality, brighter, use IPS (In-Plane Switching) technology -- which provides more accurate color even at wider viewing angles -- and have been created for optimum use with 16:9 high-definition video (the "Early 2009" models, by contrast, have a 16:10 display ratio).

The "Late 2009" models also have better speakers -- said to be "louder, clearer sound with better bass response and less distortion" and are bundled with a compact aluminum Apple Wireless Keyboard and a new multi-touch "Magic Mouse" where the "entire top is a seamless multi-touch surface" that allows one to "navigate using intuitive finger gestures". The "Early 2009" models, by comparison, have a similar wired keyboard and the comparatively simple "Mighty Mouse" (that still provides custom input, but not "multitouch" functionality).

All of these models have the same integrated "iSight" video camera. All have four USB 2.0 ports, a Firewire "800" port, built-in AirPort Extreme (802.11a/b/g/n), Bluetooth 2.1+EDR, Gigabit Ethernet, a Mini DisplayPort (which supports an external display up to 30" - 2560x1600), and optical digital audio in and out ports. However, the "Late 2009" add an SD Card slot and the 27" "Late 2009" models also support input from external DisplayPort sources (so they can be used as an external display for another DisplayPort-equipped Mac, Blu-ray player, or other device).

Internally, all of these Macs use 1066 MHz PC3-8500 DDR3 SDRAM, although the "Early 2009" models only support 8 GB of RAM and the "Late 2009" models support 16 GB of RAM. With the exception of the high-end iMac "Core i5" 2.66 27-Inch (Late 2009), which is quite different internally, architecture and clockspeeds are similar, but there are notable differences as well -- a 3 MB level 2 cache in most of the "Late 2009" line rather than 6 MB in the models replaced -- as well as different graphics processors for many configurations.

The major configuration differences between the "Late 2009" models and the "Early 2009" Aluminum model that each immediately replaced are summarized below for your convenience. Please refer to the specs page for the model of interest for complete details.

The entry-level model gained a significantly improved display (8-bit rather than 6-bit) as well as increased clockspeed (but a smaller L2 cache), more RAM, and a larger hard drive:

The low-middle range configuration may be the "least improved" as it has an LED-backlit (but smaller display) and a faster processor (but smaller L2 cache). Graphics are significantly improved by the "Late 2009" model.

The middle-high end configuration gained a faster processor (but smaller L2 cache), a larger and LED-backlit display, modestly improved graphics, a larger hard drive, and a lower offering price.

The high-end configuration gained a larger and LED-backlit display, vastly increased performance, and a lower price:

Ultimately, most users likely would be quite happy with the generally higher-quality displays and enhanced configurations provided by the "Late 2009" iMac models when compared to the models each replaced (not to mention significantly increased power at the high-end), but the "Early 2009" iMac models remain well worth consideration, particularly given lower prices on the used market.

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Please refer to the Ultimate Mac Comparison feature to dynamically compare any iMac model to any other G3 or later Mac.