Apple's kept mum on why its new iOS digital assistant Siri is limited to the iPhone 4S, but it certainly doesn't appear to be due to any hardware limitations: developer Steven Troughton-Smith has hacked a regular iPhone 4 to run the talkative service. Working with 9to5Mac, Troughton-Smith was able to install the 4S Springboard and related Siri files onto the previous-gen device, and claims the device should able to recognize spoken commands in both dictation and Siri inquiry modes. Unfortunately we can't know for sure, as the iPhone itself is only half of the Siri equation — and Apple's servers only respond to requests from supported hardware.

None of this should come as a surprise. Siri had been available as a standalone iOS app for a number of years, though development stalled after Apple bought the company in 2010. In the days leading up to the iPhone 4S launch the original app gave users a friendly reminder that it would be "leaving for home" on October 15th. Sure enough, trying to use old-school Siri now just returns a server response error. While there had been some speculation that the service had been rewritten to rely on dual-core support, or that the 4S had some dedicated voice-processing hardware on-board, iFixit found nothing that seemed strictly Siri-focused in its teardown, and Troughton-Smith's work seems to rule out the former rumor. In fact, the developer doesn't see any technical reason why the iPhone 3GS wouldn't be able to support the feature as well. Apple's decision could be part of a staggered roll-out — Siri is noted to be in beta still — or simply a business decision to incentivize upgrades. Either way, if developers are able to find a way to fool Apple's servers, a variety of iPhones may be soon running Siri, whether Cupertino likes it or not. Check out Troughton-Smith's handiwork below.