The iPhone OS 4.0 firmware was released yesterday atÂ WWDCÂ 2010 event by apple along the new iPhone 4. Now if you have an iPhone 3G or 3GS model and want to upgrade your device to the new 4.0 firmware to access the brand new features, then here is how to update iPhone 3G/3GS to 4.0 firmware. Just do the following instructions to upgrade iPhone 3G/3GS to 4.0 firmware.
1. Using the cable, connect your iPhone 3G/3GS with the computer.
2. If iTunes didn’t open up automatically, open it.
3. Choose your iPhone from the devices list.
4. Under the Summary tab, click Check for Update.
5. Choose Download and Install to upgrade iPhone 3G/3GS to 4.0 firmware.
Now the 4.0 firmware update starts. Wait till the upgrade process finishes and your iPhone 3G/3GS will be ready with the 4.0 firmware.