Where can I download 3.x firmware files for the iPhone 3GS?
Apple's iPhone 3GS shipped with the iPhone 3.0.0 operating system. On your computer, right-click the link below to download the official firmware restore file.
iPhone 3GS firmware version 3.0.0 can be found here: iPhone2,1_3.0_7A341_Restore.ipsw
iPhone 3GS 3.0.1: iPhone2,1_3.0.1_7A400_Restore.ipsw
iPhone 3GS 3.1.0: iPhone2,1_3.1_7C144_Restore.ipsw
iPhone 3GS 3.1.2: iPhone2,1_3.1.2_7D11_Restore.ipsw
iPhone 3GS 3.1.3: iPhone2,1_3.1.3_7E18_Restore.ipsw