Valve's oft-rumored "Steam Box" is making its first public appearance at CES 2013 thanks to a newly announced partnership with mini-PC maker Xi3.

Xi3 today announced "an investment from Valve Corporation" and a "new development stage computer game system," which is being showcased at both the Xi3 and Valve booths at CES this week.

The still-in-development device is optimized for computer game play on large, high-definition displays. Xi3 says that the modular computer was designed specifically to support both Steam and Big Picture mode.

"Today marks the beginning of a new era for Xi3," said Jason A. Sullivan, founder, president and CEO of Xi3. "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."

It is unclear from the initial announcement what the specs of the product are. We have reached out to both Valve and Xi3 for comment. This story is developing and we will provide updates when we find out more information.

A quick search of the Xi3 reveals that the company tried to Kickstart two new configurations of the Xi3 Modular Computer in September 2012 (X7A and X3A), but the campaign failed to meet its funding goal.

Update: We just stopped by the Xi3 booth at the Digital Experience event in Las Vegas, and came away with some more details on the project, codenamed Piston. "I can't say much," Xi3 chief marketing officer David Politis told Polygon. "I know you want to know more, but I can't say much." Here's everything Mr. Politis did tell us (and show us!), including photographs of the prototype.

Update 2: Valve officials say that Piston is one of many prototypes they're showing off at CES.