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What's inside the Piston Steam Box prototype?

Digital Foundry on what to expect from the Valve-funded mini games machine

Steam Box is real. Valve is intent on making a series of x86-based living room PCs and prototypes are present at CES 2013. Based on PC architecture and running Linux, the Piston concept from manufacturer Xi3 is an ultra-tiny metallic cube that boasts an impressive array of PC inputs and outputs and is said to draw just 40 watts from the mains - half that of an Xbox 360. It's understood that Valve itself has invested in Xi3 and that the kit is present - along with other designs - in its CES booth.

"In its current form, Piston looks like a niche device designed with form factor - rather than gaming performance - in mind."

"Today marks the beginning of a new era for Xi3," says Xi3 CEO Jason A. Sullivan. "This new development-stage product will allow users to take full-advantage of their large high-definition TV displays for an amazing computer game experience. As a result, this new system could provide access to thousands of gaming titles through an integrated system that exceeds the capabilities of leading game consoles, but can fit in the palm of your hand."

Whether this is actually going to make it to production remains to be seen, and we note the careful use of "could provide" rather than "provides" or "will provide" in Sullivan's quote.

Essentially, what we are looking at here is laptop technology sans screen and keyboard, refactored into an upgradable, modular and very, very small piece of kit. Inside the svelte cube exterior we find a rather innovative approach to PC design in that the motherboard is divided into three distinct sections arranged into a U-shape. At the bottom we find the processor control circuit board which houses the APU and RAM, flanked by two IO boards. The beauty of the design is that all three of these boards can be swapped out for other options, or upgraded. The downside is that three different mainboards are likely to cost significantly more to manufacture than a single product.

The Piston prototype is based on the Xi3 X7A, pictured here. With three video outputs, eight USB inputs and four eSATA ports we would expect any consumer unit to be pared back a little in comparison, unless Xi3 is continuing to address its ultra-niche audience.

It's the processor board itself that is the most interesting element. Shots of the interior have previously shown what looks remarkably like a desktop AMD CPU nestling at its core, but the specs for the "performance" X7A model on which the Piston is based are a complete match in every respect for the mobile Trinity APU released in laptops this year, and reviewed by Digital Foundry's Tom Morgan. AMD's APUs are essentially power-efficient multi-core processors backed by integrated graphics cores that offer the same kind of performance you'd find from an entry-level GPU. Previously regarded as something of a joke, IGPs are now being taken seriously by both Intel and AMD, with the former making significant strides with its HD4000, though AMD's offerings are well ahead when it comes to gaming performance.

"The miniscule dimensions of the Piston limit the kind of rendering power available. The device almost certainly uses a mobile version of AMD's Fusion technology."

So with 384 shader cores and a quad-core CPU that boosts up to 3.2GHz, we're essentially looking at something very much like the top-end mobile AMD Trinity core, a piece of technology we've put through its paces on the most demanding of games. Dotted throughout this article you'll see how it copes with the likes of Battlefield 3, Crysis 2 and Skyrim, but the bottom line is that there is no "next-gen" performance here - at 720p resolution, we see some improvement on the DICE classic compared to the Xbox 360 and PlayStation 3, while the results with the Crytek and Bethesda epics are somewhat inconclusive. We also need to factor in that BF3 and Crysis 2 are running at low quality settings, though we can invoke the high profile on Skyrim and still get acceptable performance. However, in all cases, we're looking at an approximate 720p30 and so we're firmly in current-gen console territory.

In a year which will be defined by the next-gen offerings from Sony and Microsoft, this places the Piston in rather a strange situation - it represents the "consolification" of a platform which is traditionally associated with massive performance gains over the dedicated games machines, but is looking decidedly sub-par compared to the hardware that is to come. Instead unique appeal lies into its ultra-tiny form factor.

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Above: Battlefield 3 running on the AMD Fusion APU almost certainly to be found in the X7A device from Xi3 on which the Piston prototype is based. The chip runs the game at low settings at around 720p30 with v-sync engaged.

However, while interesting from a broad ballpark performance aspect, what we are looking at here is Windows performance, and Valve will be running Linux. NVIDIA's Timothy Lottes (creator of FXAA and TXAA) makes some compelling arguments on his blog for the advantages that the open-source OS and OpenGL have over Windows, and it's well known that Valve has a crack team looking into gaming optimisations for the platform as well as developing tools and workflows to make porting games across simpler and easier than it is now. A point which really stands out in Lottes' comments is the fact that when a game is running on Linux it has access to the capabilities of the whole machine with no background processes eating away at performance.

"While we expect significant improvement in this year's revisions, the current-gen AMD APUs offer ballpark gaming performance with Xbox 360 and PS3."

While many won't be too impressed with a new hardware proposition that offers little in the way of a generational boost in gaming visuals over the seven-year-old Xbox 360, one factor that needs to be stressed is that the X7A hardware on which Piston is based is a modular system that can be upgraded - and that the new hardware has no definitive, locked-down specs. AMD's desktop Trinity platform (essentially identical to the notebook version, albeit with higher clock speeds) is based around a CPU socket that has been designed to be future-proof for several years, and it wouldn't surprise us at all if the same thing were true of the mobile equivalent. That being the case, it may well be that the production Piston uses the upcoming revision of the Fusion APU, which should see redesigned, more efficient CPU cores working in concert with a GPU upgrade derived from the hugely successful GCN architecture that powers all of AMD's 7xxx graphics cards. There will also be a shared memory space accessible by both the CPU and GPU elements of the processor.

In short, we could expect to see a significant bump over the performance seen with the current Trinity APU, but factoring in the tiny form factor of the unit and the low power draw inherent in the design, it's probably still going to fall some way short from what we can expect from the next-generation consoles from Sony and Microsoft, which we expect to guzzle power in comparison. Indeed, the chances are that there'll be considerably more powerful Steam Boxes out there, including the "prime" reference design box from Valve itself.

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Above: Even on the lowest detail settings, we struggled to get Crysis 2 running smoothly on the AMD Trinity laptop and needed to run at 1024x600 to get something approaching a locked 30FPS.

The direction taken with the Piston concept has drawn some sharp criticism from hardcore gamers, perhaps hoping for a Steam Box more along the lines of the Alienware X51, which these days features the latest Ivy Bridge CPUs in combination with the Nvidia GTX 660, providing a gaming experience considerably beyond current-gen consoles. Not helping matters is the fact that the price-point for the Xi3 weighs in at a wallet-worrying $999 - ballpark X51 money. Built in bulk, it's clear that this relatively simple design could be sold for a much lower price, so the real question in determining cost is how much AMD would charge for the APU: retail cost of the desktop Trinity chip is around £93 while complete laptops built around the A10-4600M aren't exactly cheap either. Any prospective Steam Box manufacturer is going to come up against the same hurdle - relatively speaking, off-the-shelf silicon isn't cheap unless you have the buying power of Dell or HP behind you.

"While Piston may address a high-end niche, we expect Valve's own box to offer a superior price to performance ratio, similar to our own Digital Foundry PC."

Of course, the fact that the Xi3 has received Valve funding and that the Piston is an element of the firm's CES booth doesn't necessarily mean that this is the Steam Box - we still expect to see a unit with a more gamer-friendly performance to price ratio. Gabe Newell has made it clear that it is just one of a number of prospective models, and there's a chance that Xi3's model may never actually come to market at all in its current form. Perhaps it's no surprise then that Valve's Doug Lombardi has also sought to contain the Piston story. While not denying the Valve connection, the prototype doesn't even warrant a mention in his comments to the press. "Valve will be at CES to meet with hardware and content developers in our booth space," he told Polygon. "We are bringing multiple custom (hardware) prototypes as well as some off-the-shelf PCs to our CES meetings." Lombardi clarified those designs, describing them as "low-cost, high-performance designs for the living room that are great candidates for Steam and Big Picture".

With the power of the Steam brand behind it though, it's safe to say that Valve will have many suitors looking to provide hardware, and the whole point of embracing Linux in the first place is to create the open platform that Gabe Newell and his colleagues believe is in jeopardy with the release of Windows 8. It's going to be very interesting to see how all this develops...

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Above: Skyrim could run at 720p on high quality settings on the AMD Trinity APU with FXAA engaged, but frame-rate struggles in places.

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Richard Leadbetter avatar
Richard Leadbetter: Rich has been a games journalist since the days of 16-bit and specialises in technical analysis. He's commonly known around Eurogamer as the Blacksmith of the Future.
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