21″ iMac (Late 2009)

The big news: Apple has introduced new screen sizes and a new display aspect ratio. The Late 2009 iMac comes in 21.5″ and 27″ sizes, and the displays have the same 16:9 aspect ratio as HDTV (the Early 2009 iMac had 20″ and 24″ 16:10 aspect ratio displays). The smaller iMac has the same 1920 x 1080 pixel size as 1080i high-def television.

Late 2009 iMacs

The Late 2009 iMac is LED backlit, and one feature new to Apple’s desktop line is a built-in SD Card slot, which is on the right side below the SuperDrive.

Visually, the screen looks even bigger, as the glass now goes all the way to the edge of the computer – no more aluminum border around the display. And the back is now aluminum instead of black plastic.

Apple has simplified things by starting the iMac with a 3.06 GHz Core 2 Duo and offering a 3.33 GHz Core 2 Duo as a build-to-order option. 4 GB of RAM is now standard across the line, and maximum RAM doubles to 16 GB (vs. 8 GB for the previous model) using four 4 GB modules.

The base 21.5″ model uses the same Nvidia GeForce 9400 GPU found in most current Macs, and the step-up model has ATI Radeon HD 4670 graphics with 256 MB of dedicated memory. This GPU is also used in the base 27″ model, and the top-end iMac has ATI Radeon

The Late 2009 iMacs have 4 USB 2.0 ports (one more than before), FireWire 800 (but not 400), gigabit ethernet, 802.11n WiFi, Bluetooth 2.1+EDR, an SD Card slot, and an 8x SuperDrive – as well as a slim keyboard with two USB 2.0 ports. This is the first Mac to ship with Apple’s Magic Mouse.

The entry-level iMac has 4 GB of RAM, a 500 GB hard drive, an 8x SuperDrive, Nvidia GeForce 9400M graphics, and Apple’s aluminum keyboard and Magic Mouse. 256 MB of system RAM is dedicated to video. All the other models have GPUs with dedicated video memory. The more powerful iMacs include a 1 TB hard drive.

These iMacs shipped with OS X 10.6.1 Snow Leopard, and they are the oldest iMacs supported by macOS Sierra.

Intel-based Macs use a partitioning scheme known as GPT. Only Macintel models can boot from GPT hard drives. Both PowerPC and Intel Macs can boot from APM (Apple’s old partitioning scheme) hard drives, which is the format you must use to create a universal boot drive in Leopard. PowerPC Macs running any version of the Mac OS prior to 10.4.2 cannot mount GPT volumes. PowerPC Macs won’t let you install OS X to a USB drive or choose it as your startup volume, although there is a work around for that.


  • introduced 2009.10.20 at US$1,199 (21.5″ GeForce 9400) and US$1,499 (21.5″ Radeon 4670); replaced by Mid 2010 iMac on 2010.07.27
  • Part no.: MC508 (Nvidia), MC509 (Radeon)

Mac OS

  • Requires Mac OS X 10.6.1 Snow Leopard or later. macOS 10.4 Mojave and later are not supported.
  • Mac OS X 10.6 Snow Leopard compatibility
    • Grand Central Dispatch is supported.
    • 64-bit operation is supported.
    • OpenCL is supported.
  • OS X 10.8 Mountain Lion compatibility
    • AirPlay Mirroring is not supported.
    • AirDrop is supported.
    • Power Nap is not supported.

Core System

  • CPU: 3.06/3.33 GHz Intel Core 2 Duo
  • L2 cache: 3 MB shared cache on CPU (6 MB on 3.33 GHz model)
  • Bus: 1066 MHz
  • RAM: 4 GB, expandable to 16 GB using four 1066 MHz DDR3 SDRAM
  • Performance, Geekbench 3:
    • 32-bit single core: 1630 (3.06 GHz), 1806 (3.33 GHz)
    • 32-bit multicore: 2913 (3.06 GHz), 3244 (3.33 GHz)
    • 64-bit single core: 1762 (3.06 GHz), 1974 (3.33 GHz)
    • 64-bit multicore: 3160 (3.06 GHz), 3550 (3.33 GHz)


  • GPU: Nvidia GeForce 9400M, used 256 MB of system RAM RAM, supports up to 1920 x 1200 external digital display, 2048 x 1536 analog display, and monitor spanning
  • GPU: ATI Radeon HD 4670 with 256 MB dedicated VRAM
  • Display: 21.5″ 1920 x 1080 LED backlit flat panel display
  • Video out: Mini DisplayPort, DVI and VGA with optional adapters


  • drive bus: 3 Gbps SATA Rev. 2
  • Hard drive: 500 GB/1 TB 7200 rpm SATA drive
  • SuperDrive: writes DVD±R, DVD+R, and DVD+RW discs at up to 8x speed, DVD-RW at up to 6x; dual layer at up to 4x; reads DVDs at up to 8x, writes CD-R discs at up to 24x, writes CD-RW discs at up to 16x, reads CDs at up to 24x


  • USB: 4 USB 2.0 ports
  • FireWire 400: none
  • FireWire 800: 1 port, 7 Watts
  • Ethernet: 10/100/gigabit
  • WiFi: 802.11n AirPort Extreme built in
  • Bluetooth 2.1: included
  • IR receiver: supports Apple Remote (not included)
  • Microphone: internal
  • Modem: No longer offered by Apple


  • Power supply: 200W
  • H x W x D: 17.75 x 20.8 x 7.42 in/45.1 x 52.8 x 18.85 cm
  • Weight: 20.5 lb/9.3 kg
  • Model identifier: iMac10,1

CPU Upgrades

  • none

Online Resources