The mystery as to why Siri is exclusive to the iPhone 4S just got a little more interesting. 9to5Mac ported the voice command system from the iPhone 4S to the iPhone 4. In the video below, developer Steven Troughton-Smith demonstrates how Siri looks on the device.
9to5 claims it can recognize spoken commands and speak back to the user. The only problem is Apple's servers are not authenticating commands from the iPhone 4 hardware. Apple fans have been debating whether other iOS devices like the iPad 2 can handle Siri's AI. 9to5's discovery proves there are no technical reasons for Siri being exclusive to the iPhone 4S.
"The iPhone 4 hardware can support the Siri artificial intelligence system, as the A4 processor is said to be powerful enough. We are not entirely sure why Apple is making Siri an iPhone 4S exclusive but it could be due to special microphone support, or because the A5 may allow it to run slightly quicker."
9to5 also noted Siri runs a little "sluggish" in their video. This is because the GPU driver for the iPhone 4 is missing.UPDATE: Newer video of Siri working more smoothly.