Valve just announced that it will ship Steam Machine prototypes to 300 beta testers on 13 December. What's more interesting, though, is that Valve will also make Steam OS available to everyone to download on that same day.

"The time has come! We are ready to begin shipping Steam Machines and Steam Controllers to the 300 selected beta participants," wrote Valve in a community blog post. "SteamOS will be made available when the prototype hardware ships. It will be downloadable by individual users and commercial OEMs."

Unfortunately, for most eager Steam fans anyway, Valve recommended that gamers wait to download and install the new operating system: "Unless you’re an intrepid Linux hacker already, we’re going to recommend that you wait until later in 2014 to try it out."

Still, plenty of reports should surface in the next few weeks about SteamOS, providing a more detailed look at how it works, performs and feels. Valve is expected to make announcements at CES 2014, too. Specifically, it should reveal Steam Machine partners on 6 January - so stay tuned for that.

READ: Valve's pursuit of the living room using Steam: Everything you need to know

SteamOS is an operating system built around Steam. It uses Linux as an architecture, though the development team at Valve has built on top. The beauty of SteamOS is that it's free; you won't need Valve hardware to install it. Valve also plans to make it a freely licensable operating system for manufacturers. So, think Android, in this regard.

SteamOS will be available for all to download on Valve's own machines as well, but the company wants to take the approach of making pre-set hardware. It therefore introduced the Steam Machines platform - which is essentially the Steambox we've heard about for years - last autumn.

Those 300 beta participants (US-only) who were hand-picked by Valve to test the Steam Machine, they'll get their notification at around 5pm EST today. Lucky.