iPhone 4

• The iPhone 4 is the first generation to include Apple's 1GHz A4 processor. It also includes 512 MBs of RAM. The phone comes with the option for 16 or 32 GBs of storage.
  
  

iPhone 3GS

• The iPhone 3GS includes the ARM Cortex A8 600 MHz processor, and features 256 MBs of RAM and the choice of 8, 16 or 32 GBs of storage.
  
  

iPhone 3G

• The 3G model used the ARM 11 412 MHz processor with 128 MBs of RAM, and came with the option for 8 or 16 GBs of storage.