What are all the differences between the "Late 2012" Aluminum iMac models?

Please note that the "Late 2012" Aluminum iMac models have been discontinued. However, this Q&A has been updated subsequently and can be quite helpful for anyone buying or selling one of these systems on the used market.

With even a fairly detailed external inspection, it would be easy to conclude that the 21.5-Inch and 27-Inch "Late 2012" Aluminum iMac models are differentiated primarily by display size.

Although display size is one obvious difference between the 21.5-Inch models -- the standard iMac "Core i5" 2.7 21.5-Inch and "Core i5" 2.9 21.5-Inch, and CTO "Core i7" 3.1 21.5-Inch -- and the 27-Inch models -- the standard iMac "Core i5" 2.9 27-Inch and "Core i5" 3.2 27-Inch and CTO "Core i7" 3.4 27-Inch -- there also are other critical differences that are important to evaluate and understand.

Photo Credit: Apple, Inc. (21.5" & 27" Tapered Edge iMac, Left & Right, Respectively)

External Differences

Each of the "Late 2012" iMac models use an all aluminum enclosure that sharply taper to a mere 5 mm at the edges of the display. In promotional copy, Apple notes that the front and back of these iMac models are so thin that the company had to implement "friction-stir welding" -- which uses a "combination of intense friction-generated heat and pressure to intermix the molecules of the two aluminum surfaces" and bond them together seamlessly. By default, neither the 21.5-Inch or 27-Inch models are VESA compliant, but each could be configured with a wall mount option instead of the aluminum stand at the time of purchase.

The 21.5" and 27" models both have "anti-reflective" 8-bit 16:9 LED-backlit TFT Active Matrix LCDs with different native resolutions -- 1920x1080 and 2560x1440, respectively. Both use IPS (In-Plane Switching) technology, which provides more accurate color than displays without IPS and each have a glass cover that is fully laminated to the LCD itself, which means that reflections are reduced, but that it is not possible to replace the display or the glass independently from one another.

Both models have an integrated 720p "FaceTime HD" webcam at the top of the display, speakers integrated at the bottom edge of the display, and dual integrated microphones. Neither has an integrated optical drive, although an external one may be added at additional cost (site sponsor Adorama has the official external Apple SuperDrive for US$79 and Other World Computing has a variety of third-party external optical drive options).

By default, each "Late 2012" iMac includes a notebook size aluminum wireless keyboard without a numeric keypad and the choice of either a wireless "Magic Mouse," where the "entire top is a seamless multi-touch surface" that allows one to "navigate using intuitive finger gestures" or a "Magic Trackpad" that provides multi-touch input like on a recent Apple notebook (both the "Magic Mouse" and "Magic Trackpad" could be purchased together for an additional US$69).

Connectivity Differences (or Lack Thereof)

Connectivity is identical on all "Late 2012" iMac models. All of these systems have an SDXC-capable SD card slot, four USB 3.0 ports, two Thunderbolt ports, built-in "MIMO" 450 Mbit/sec 802.11a/b/g/n wireless networking (which Apple used to refer to as AirPort Extreme), Bluetooth 4.0, Gigabit Ethernet, and a single "headphone/optical digital audio output (minijack)" that also supports the Apple iPhone headset with microphone.

Both of the Thunderbolt ports are capable of powering an external display up to 30" (2560x1600) -- so all of the "Late 2012" iMac models can support two external displays simultaneously along with the internal display -- or other peripherals that support the Thunderbolt standard. The "Late 2012" iMac models also support "Target Display Mode" from external Thunderbolt-equipped sources so they can be used as an external display from another Thunderbolt-equipped Mac.

Identification Differences

The "Late 2012" iMac models with the same display size share model numbers and model identifiers.

Specifically, the 21.5-Inch models share model number A1418 and the 27-Inch models share model number A1419. However, the model number is not precise enough to uniquely identify specific models, which is important for many tasks like upgrading the RAM.

Externally, the EMC number is better for more unique identification as it is less likely to be shared by future models using the same case type. The 21.5-Inch and 27-Inch "Late 2012" iMac models are EMC number 2544 and 2546, respectively. Just as the site has for other models for many years, EveryMac.com has meticulously hand documented these details for your convenience.

In software, the 21.5-Inch models share the iMac13,1 model identifier whereas the 27-Inch models share the iMac13,2 model identifier and this identifier also is sufficiently unique for upgrades.

Finally, EveryMac.com's Ultimate Mac Lookup feature additionally can uniquely identify each one of the "Late 2012" iMac models by their serial numbers.

Internal Differences

Internally, by default, all "Late 2012" iMac models use "Ivy Bridge" Core i5 Quad Core processors mounted on an LGA 1155 (H2) processor socket, but some models can be custom configured with an "Ivy Bridge" Quad Core Core i7 processor, as well. Each also has a "Direct Media Interface" (DMI) that "connects between the processor and chipset" in lieu of a traditional system bus that Intel reports runs at 5 GT/s. All of these systems use NVIDIA "Kepler architecture" graphics, but the capabilities are different.

Both lines support 204-pin 1600 MHz PC3-12800 DDR3 SDRAM SO-DIMMs, although the 21.5-Inch models only have two RAM slots and support 16 GB of RAM whereas the 27-Inch models have four RAM slots and support 32 GB of RAM. Officially, Apple does not intend for one to upgrade the RAM in the 21.5-Inch models after initial purchase at all -- and doing so is unnecessarily complicated -- but it is possible. The 27-Inch models, by contrast, have a "pop off" door on the back that makes upgrading the RAM quick and easy.

Both lines support a single 2.5" 6 Gb/s Serial ATA (Revision 3.0) hard drive or SSD. It is possible to upgrade the storage on all of these models, but it is not easy.

Comparison Chart

The major differences between the four stock "Late 2012" 21.5" and 27" iMac models -- size, display, processor, graphics, and RAM upgrade methods -- as well as configuration, identifiers, and original price -- are summarized below:

iMac "Late 2012"	2.7 21.5"	2.9 21.5"	2.9 27"	3.2 27"
Std. Processor Speed:	2.7 GHz	2.9 GHz*	2.9 GHz	3.2 GHz**
Std. Processor Type:	Core i5	Core i5*	Core i5	Core i5**
Std. Processor No:	3330S	3470S*	3470S	3470**
Std. Processor Cores:	4	4	4	4
Turbo Boost:	3.2 GHz	3.6 GHz	3.6 GHz	3.6 GHz
Hyper-Threading:	No	No*	No	No**
L2 Cache:	256k x4	256k x4	256k x4	256k x4
L3 Cache:	6 MB	6 MB*	6 MB	6 MB*
Std. Hard Drive:	1 TB (5400)	1 TB (5400)	1 TB (7200)	1 TB (7200)
Std. RAM:	8 GB	8 GB	8 GB	8 GB
Max. RAM:	16 GB	16 GB	32 GB	32 GB
RAM Upgrade:	Difficult (Hack)	Difficult (Hack)	Easy (Door)	Easy (Door)
Video System:	GT 650M	GT 650M	GTX 660M	GTX 675MX†
Video Type:	GDDR5	GDDR5	GDDR5	GDDR5
Video Memory:	512 MB	512 MB	512 MB	1 GB†
Optical Drive:	None	None	None	None
Display Size:	21.5-Inch	21.5-Inch	27-Inch	27-Inch
Native Resolution:	1920x1080	1920x1080	2560x1440	2560x1440
Apple Order No (US):	MD093LL/A	MD094LL/A	MD095LL/A	MD096LL/A
Apple Model ID:	iMac13,1	iMac13,1	iMac13,2	iMac13,2
EMC Number:	2544	2544	2546	2546
Original Price (US):	US$1299	US$1499	US$1799	US$1999

* By custom configuration, the iMac "Core i5" 2.9 21.5-Inch could be configured with a 3.1 GHz Quad Core "Core i7" processor (I7-3770S) for an extra US$200. This "Core i7" processor supports Hyper-Threading (it has two threads per core for a total of eight threads for the system) as well as Turbo Boost 2.0 (the system can dynamically increase the processor clockspeed to 3.9 GHz when tasks demand). It has a larger 8 MB level 3 cache, too. EveryMac.com also has documented this custom configuration as its own model.

** The iMac "Core i5" 3.2 27-Inch also could be configured with a 3.4 GHz Quad Core "Core i7" processor (I7-3770) for an extra US$200. This "Core i7" processor supports Hyper-Threading (it has two threads per core for a total of eight threads for the system) as well as Turbo Boost 2.0 (the system can dynamically increase the processor clockspeed to 3.9 GHz when tasks demand). It has a larger 8 MB level 3 cache, too. EveryMac.com also has documented this custom configuration as its own model.

† At the time of purchase, this model could be custom configured with a NVIDIA GeForce GTX 680MX with 2 GB of dedicated GDDR5 memory for an extra US$150.

Used iMac Purchase Options

There are any number of places to purchase a used "Late 2012" iMac. However, purchasing from a quality vendor with extensive experience in the Mac market -- and after sales support -- will provide the best experience and save you money and time, too.

In the US, site sponsor Adorama sells new iMac models with free shipping. Other World Computing sells used and refurb iMac models at bargain prices with free shipping, as well. Finally, if you need to sell an iMac, A+ BBB-rated Cash for Your Mac will buy your older iMac with an instant quote and prompt payment.

In the UK, site sponsor Hoxton Macs sells used iMac models with a one-year warranty and free next day delivery throughout the UK. Delivery across Europe also is available starting at just £9.99 for two-day delivery to France and Germany.

Please also see EveryMac.com's Ultimate Mac Comparison feature to dynamically compare any iMac model to any other Mac.