Why is everyone so amazed that the Apple TV runs iOS? True, Apple itself has never said as much, but anyone who has looked at the product's tech specs on the Apple website - posted almost immediately after the device's announcement - will see that it's based on Apple's A4 CPU.

The A4 is, of course, the ARM-based system-on-a-chip Apple uses in the iPhone 4, the iPad and the latest iPod Touch. All these devices run iOS.

Apple may have its bonkers moments, but we can't honestly see it recompiling Mac OS X 10.4 - the original Apple TV's operating system - for ARM processors. It's much easier to port the UI across and load it in place of Springboard, the usual iOS user interface.

So, iOS is Apple's OS for ARM. A4 is ARM. Apple TV has A4. Therefore Apple TV has iOS.

QED.

Of course, the new Apple TV may not run the full implementation of iOS, but there's surely enough code in there to support the introduction of downloadable apps. And, as some hope, the ability to jailbreak the thing.

Like its predecessor, the new Apple TV has a USB port - mini this time - for "service and support", as Apple puts it. That potentially provides a door to allow a patchstick to be connected from which the box will boot and run code that tweaks the on-board OS to allow SSH access and such.

We used such a method to install the XMBC open source media centre UI on our old Apple TV this weekend, and it works a treat, playing back movies stored on local network file shares perfectly. ®