I'm not talking about the Xi3 Piston or other hardware, but the Linux-based Steam game console coming from Valve -- the console that Valve hopes to be pushing out for testing in the coming months.
The information in this post are my thoughts on the hardware that may be part of the Steam Box and not any official communication from Valve on the subject matter. Namely, my view on the hardware that would work best for a Linux-based gaming platform based upon being the lead in monitoring and performance testing of Linux enthusiast/gamer hardware for nearly the past decade.
First of all, for those wondering about the Valve Linux game benchmarks I've talked about before, they're still being worked on. The Steam command-line arguments aren't working incredibly nice last time I checked some weeks ago with automatically exiting the client after the benchmark demo has been completed, which is needed for fully automating the tests in a reproducible way through the Phoronix Test Suite. Soon as the automated benchmarking is working great and reliably through Steam, benchmark results for a range of hardware will come, but the information shared in this article is based upon my informal Source Engine testing on Linux and the feedback of other Linux gamers.
A Special Linux Delivery At Valve Software -- I was hand-delivering beer to Valve Linux developers back even before many people believed my exclusive Phoronix reports about Valve's Linux interest and plans.
The AMD Catalyst driver has come a long way over the past decade, but in recent years the quality seems to have regressed overall. The OpenGL performance is still generally on par with Microsoft Windows and there's a near feature parity to the Windows driver, but the most recent round of problems I've run into has been OpenGL bugs (e.g. with a Radeon HD 7850 review being worked on at the moment, the latest Catalyst has regressed badly for Unigine) and other strange driver issues (e.g. the unsupported hardware watermark, EDID/monitor issues, etc).
Valve is a company about quality and for a Linux gaming solution there really is no other choice to think about besides Catalyst. The AMD Catalyst driver isn't always reliable and the open-source Mesa/Gallium3D drivers simply won't cut it. The open-source Intel/AMD/Nouveau drivers are living in an OpenGL 3.1 world, they face patent issues with S3TC and other features, and their performance is usually a long-shot from the proprietary drivers.
Though due to hardware design and pricing, they might end up with an AMD Radeon graphics processor, but hopefully we will see some NVIDIA Kepler derived solution for the console that's supposed to be shipping before year's end. NVIDIA hardware has been the graphics vendor of choice to most Linux desktop users going back to the early 2000's.
Another good reason for going with NVIDIA hardware would be for their PureVideo HD engine that is exposed under Linux via VDPAU. NVIDIA's VDPAU implementation generally works fantastic and is what I have found to be the best for hardware-based video playback acceleration on Linux. If the Steam Box is to go against the Sony PlayStation 4 and next-generation Xbox, it will need a compelling multimedia story.
What would be really interesting was if the Steam Box employed a NVIDIA Optimus-like solution. Power consumption, heat, and noise are very important for these living room game consoles. A high-performance discrete GPU isn't needed for video playback and very lax games, but Intel HD 4000 "Ivy Bridge" graphics or Haswell would be more than enough for those lighter-weight workloads. Intel graphics support on Linux is good, but their integrated graphics can't compete with high-end NVIDIA/AMD GPUs.
Right now the NVIDIA Linux driver doesn't provide any Optimus support, but NVIDIA engineers have been working on it. With pressure from Valve and promised chip sales, Optimus could happen for Linux. NVIDIA may also be trying hard to get its chips in the Steam Box given Sony going with Radeon graphics and Microsoft's Xbox "Durango" also having been rumored to rely upon Radeon graphics.
Memory: The PlayStation 4 has 8GB of system memory and the next-generation Xbox also looks that way too, in which case I would expect Valve to match that or at least provide 4GB. I haven't hit any memory pressure issues with the Valve's games on Linux.
Disk: The Steam Box will be an entirely disc-less solution, with Valve obviously wanting gamers to be purchasing titles digitally through Steam. Storage will obviously be a big deal and those with slower Internet connections won't be wanting to deal with re-downloading titles each time they wish to play. Fortunately, there's Linux file-systems that deal well with transparent disk compression and other features. I would expect the Steam Box to be backed by at least 128GB of storage if not 256GB or even 512GB in a deluxe console. This is storage likely backed by a solid-state drive.
Controller: All I know at this point is that Valve is reported to be testing a few different controller designs. Though I would be on the look-out for any new Linux kernel input drivers proposed for mainline inclusion in the coming months.
SDK: On the software side, it will be interesting to see how Valve deals with a Software Development Kit for their Steam Box. Ideally, the Steam Box Linux platform will be fairly vanilla. In this case, if porting to the Steam Box would mean "free" compatibility with the Linux desktop. It would be very sensible if Valve were to target OpenGL 3/4 for graphics rendering. A big win -- and good news for desktop compatibility -- would be Valve promoting SDL as the library for handling audio, input, and other functionality. SDL is already cross-platform and used by some Valve software. Sam Lantinga, one of the lead SDL developers, is working for Valve.