Siri, the voice-based personal assistant software that Apple would only let us run on the iPhone 4S has this weekend seen itself ported to the more modestly specced iPhone 4 and fourth-gen iPod touch. Performance is identical on the older devices to what it is on the 4S, inviting the conclusion that considerations outside of pure hardware capabilities — such as the cost and scale of supporting Siri server requests from the millions of compatible devices — led to the decision to limit the service to the latest smartphone. Unfortunately, while this hack is working perfectly well for its makers, the familiar suspects of Steve Troughton-Smith and chpwn, it isn't being released due to the complexity of prep work required and because it hasn't yet been thoroughly tested. Steve informs us on Twitter that full details will be forthcoming after an iPhone 4S jailbreak has been released by the community. 4S owners are still, therefore, the only ones able to enjoy the aid of Siri, though the patient iPhone 4 or iPod touch user looks likely to soon be joining those ranks as well.