20″ iMac (Early 2008)

Apple updated the iMac with Intel’s more efficient Penryn processor in April 2008, which has a larger Level 2 cache and includes the SSE4.1 instruction set. The Early 2008 iMac has also moved from the 800 MHz system bus in the Mid 2007 iMac to 1066 MHz, and clock speeds on the 20″ model range from 2.4 GHz to 2.66 GHz.

20" Aluminum iMac

The aluminum iMacs have three USB 2.0 ports, FireWire 400 and 800 ports, gigabit ethernet, 802.11n WiFi, Bluetooth 2.1+EDR, and an 8x SuperDrive – as well as a slim keyboard with USB 2.0 ports. This was the last iMac to use an Ultra ATA interface for its optical drive.

2008 iMac

The 20″ 2.4 GHz iMac has 1 GB of RAM, a 250 GB hard drive, an 8x SuperDrive, Radeon HD 2400 XT graphics, AirPort Extreme, Bluetooth, and Apple’s aluminum keyboard and Mighty Mouse.

The 2.66 GHz model ships with 2 GB of RAM, a 320 GB hard drive, and use Radeon HD 2600 Pro graphics. The Early 2008 iMac ships with Mac OS X 10.5.2 Leopard and iLife ’08. The Early 2008 iMacs support OS X 10.11 El Capitan.

Although it is not officially supported, the Early 2008 iMac can run macOS Sierra using Colin Mistr’s Sierra Patch Tool. However, WiFi is not supported on this device. See our macOS Sierra page for more details and a link.

What You Need to Know

While you can run OS X 10.5 Leopard with 1 GB of system memory, it runs much more smoothly with 2 GB, and 2 GB is a realistic minimum for OS X 10.6 Snow Leopard. You can run OS X 10.7 Lion with 2 GB, but it needs 4 GB to flex its muscles. OS X 10.8 Mountain Lion and 10.9 Mavericks run poorly with 2 GB and improve drastically with 4-6 GB. OS X 10.10 Yosemite and OS X 10.11 El Capitan really want the 6 GB maximum this model supports.

Note that 20″ aluminum iMacs use an 18-bit LCD, which can only display 262,144 colors, not the “millions” all other iMacs can display. This should be good enough for most users.

Unlike earlier iMacs, where every USB port could provide 500 mA of power, only a single high-powered device can be attached to the USB ports, and software will enable one of its downstream ports to supply 500 mA of power. If a second high-powered device is attached, it will behave like a normal bus-powered hub and only provide 100 mA per downstream port.

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 2008.04.28 at US$1,199 (2.4 GHz) and US$1,499 (2.66 GHz); replaced by Early 2009 iMac on 2009.03.03
  • Model no.: A1224
  • Part no.: MB323 (2.4 GHz), MB324 (2.66 GHz)
  • Model identifier: iMac8,1

Mac OS

  • requires Mac OS X 10.5.2 Leopard through 10.11 El Capitan, macOS Sierra via patch tool – see macOS Sierra on Low End Macs. Broadcom BCM4321 WiFi module, if present, is not supported by Sierra. Some Early 2008 iMacs have an audio issue that will not let you adjust sound volume in Sierra. 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 not supported except with the GeForce 8800 GS GPU.
  • OS X 10.8 Mountain Lion compatibility
    • AirPlay Mirroring is not supported.
    • AirDrop is not supported.
    • Power Nap is not supported.
  • OS X 10.10 Yosemite compatibility
    • AirDrop is not supported.
    • AirPlay Mirroring is not supported.
    • Handoff is not supported.
    • Instant Hotspot is not supported.
    • Power Nap is not supported.

Core System

  • CPU: 2.4/2.66 GHz Intel Core 2 Duo “Penryn”
  • L2 cache: 6 MB shared cache on CPU
  • Bus: 1066 MHz
  • RAM: 1 GB (2.4 GHz) or 2 GB (others), officially expandable to 4 GB using two PC-6400 DDR2 SODIMMs but capable of using 6 GB.
  • Performance, Geekbench 3:
    • 32-bit single core: 1470
    • 32-bit multicore: 2732
    • 64-bit single core: n/a
    • 64-bit multicore: n/a


  • Graphics, 2.4 GHz: ATI Radeon HD 2400 XT with 128 MB RAM (256 MB optional), supports up to 1920 x 1200 external digital display, 2048 x 1536 analog display, and monitor spanning
  • Graphics, 2.66 GHz: ATI Radeon HD 2600 Pro with 256 MB RAM, supports up to 1920 x 1200 external digital display, 2048 x 1536 analog display, and monitor spanning
  • Display: 20″ 1680 x 1050 flat panel display (18-bit LCD)
  • Video out: mini-DVI, VGA, S-video, composite (requires adapter)


  • Hard drive bus: 3 Gbps SATA Rev. 2
  • Hard drive: 250/320 GB 7200 rpm SATA drive
  • Optical drive bus: Ultra ATA/100 (operates at UATA/33 or UATA/66)
  • 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: 3 USB 2.0 ports, only 1 high-powered device device allowed
  • FireWire 400: 1 port, 7 Watts
  • FireWire 800: 1 port, 7 Watts
  • Modem: optional 56 kbps USB modem supports v.92
  • Ethernet: 10/100/gigabit
  • AirPort Extreme: 802.11n
  • Bluetooth 2.1: included
  • IR receiver: supports Apple Remote (included)
  • Microphone: internal


  • Power supply: 200W
  • H x W x D: 18.5 x 19.1 x 7.4 in/46.9 x 48.5 x 18.9 cm
  • Weight: 20 lb/9.1 kg

CPU Upgrades

  • none

Online Resources

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Short link: http://goo.gl/uD5ryl

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