iMac 21.5"

2.5GHz quad-core Intel Core i5 with 6MB on-chip shared L3 cache  
or
2.7GHz quad-core Intel Core i5 with 6MB on-chip shared L3 cache

500GB (7200 rpm) hard drive   or   1TB (7200 rpm) hard drive
AMD Radeon HD 6750M graphics processor with 512MB of GDDR5 memory
or
AMD Radeon HD 6770M graphics processor with 512MB of GDDR5 memory

• Communication Ports
• One Thunderbolt port on 21.5-inch iMac
• Two Thunderbolt ports on 27-inch iMac
• Mini DisplayPort output with support for DVI, VGA and dual-link DVI (adapters sold separately)
• One FireWire 800 port; 7 watts
• Four USB 2.0 ports
• SDXC card slot
• Slot-loading 8x SuperDrive with 4x double-layer burning (DVD±R DL/DVD±RW/CD-RW)
• Audio in/out
• 10/100/1000BASE-T Gigabit Ethernet (RJ-45 connector)
• IR receiver