Today at CES 2014, Asus was all about the twofers. First, the company showed off its upcoming PadFone X, which is a 5-inch Android phone that slides inside a 9-inch touchscreen tablet. The tablet has no processor of its own, but uses the brains of the phone and provides an additional battery for recharging.

Asus will launch the product "sometime" this year, with AT&T as its exclusive carrier. The device has echoes of the Motorola Atrix Lapdock that was launched at CES a few years ago. But that device never caught on, because of the awkward adaptation of the Android interface to a special laptop mode and an accessory price that made the Lapdock almost as expensive as a real laptop.

There's no word on pricing yet for the PadFone X, but if Asus and AT&T can make the price competitive with other 5-inch phones without charging an extra arm and a leg for the tablet screen, it may be a far more successful device than the Atrix Lapdock.

For all the show news, trends, and analysis, visit our insider's guide to CES 2014.

Asus also announced an update to its Transformer line of tablet-laptop hybrids, the 13-inch Transformer Book Duet TD300. The company actually calls it a 4-in-1 device, because not only does the screen split from the keyboard, it also runs both Google’s Android OS as well as Microsoft’s Windows 8.

The Book Duet TD300 can switch between operating systems in about 6 seconds, and also has a shared folder that can migrate content between Android and Windows. Inside is a single Intel Core I-series chip, and an optional extra hard drive in the keyboard, although, surprisingly, no extra battery. Available later this year, it will start at $600.

—Glenn Derene

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