It's a dual-core chip, but features Hyperthreading, so has four virtual cores. Its rated clock speed is 1.9GHz, but it can be pushed all the way to 3GHz with Intel's Turbo mode.
Perhaps most importantly for a laptop with a 1080p display, it's an Ivy Bridge chip, and so features Intel's latest and greatest integrated graphics. HD Graphics 4000 might not trouble a dedicated card for grunt, but it's plenty powerful for HD video and casual gaming.
Along with the processor, you get 4GB of DDR3 RAM, clocked at a healthy 1600MHz. While this should be plenty for standard Windows use, this amount of RAM - along with the dual-core processor - are a reminder that this isn't intended to be a portable workstation.
The solid state drive is SATA 3, so is capable of taking advantage of the speeds of its flash memory. The 256GB should be enough for most people, but that's not what you get in practice - only 140GB is available for data. This is likely to prove to be an issue for those with large music or video collections.
It's a handy thing, then, that Asus has included two USB 3.0 ports, making it easy to transfer files to and from the Zenbook Prime very, very quickly.
Bluetooth 4.0 is also included, and there's built-in Wi-Fi, of course. There's no Ethernet port, most likely for size reasons, but you can buy an adaptor.
Speaking of adaptors, the micro HDMI and mini VGA ports offer video output, but you'll need to make sure you have the correct connectors, since neither is included in the box.
Of course, the Asus Zenbook Prime UX31A's own screen is nothing to be sniffed at. It's a 1080p IPS display - something you rarely see in 13-inch laptops at all, let alone in Ultrabooks. Though it doesn't quite reach the extreme pixel density of Apple's MacBook Pro with Retina display, it's still an extremely high resolution for the screen size. And, being a Full HD display, it's 16:9, so is ideal for watching movies and TV shows on.
Adding to the multimedia credentials is the Bang & Olufsen-powered speaker system.
There's no optical drive, though. This is hardly surprising for such a thin machine, but it does mean you can't make use of that Full HD display to play Blu-rays without buying an external drive.