http://www.apple.com/imac/ Processor and memory 21.5-inch models, one of the following: 3.06GHz Intel Core i3 processor with 4MB level 3 cache; supports Hyper-Threading 3.2GHz Intel Core i3 processor with 4MB level 3 cache; supports Hyper-Threading and Turbo Boost 3.6GHz Intel Core i5 processor with 4MB level 3 cache; supports Hyper-Threading and Turbo Boost 27-inch models, one of the following: 3.2GHz Intel Core i3 processor with 4MB level 3 cache; supports Hyper-Threading and Turbo Boost 3.6GHz Intel Core i5 processor with 4MB level 3 cache; supports Hyper-Threading and Turbo Boost 2.8GHz Quad-Core Intel Core i5 processor with 8MB level 3 cache; supports Turbo Boost 2.93GHz Quad-Core Intel Core i7 processor with 8MB level 3 cache; supports Hyper-Threading and Turbo Boost 4GB (two 2GB SO-DIMMs) of 1333MHz DDR3 SDRAM; four SO-DIMM slots support up to 16GB Configure your iMac now, only at the Apple Online Store. Storage5 21.5-inch models: 500GB or 1TB 7200-rpm Serial ATA hard drive Optional 2TB 7200-rpm Serial ATA hard drive 27-inch models: 1TB 7200-rpm Serial ATA hard drive Optional 2TB 7200-rpm Serial ATA hard drive Optional 256GB solid-state drive -- watchman