Xi3 Piston, the first device revealed when Valve admitted it was getting into hardware, is not a Steam Machine - because "if you can play it on a computer you should be able to play it on a Piston".
UPDATE: The team at Xi3 have contacted VG247 to state that the Piston is in fact an upgradable machine, stating: "by using three interconnected boards within the PISTON Console to replace the standard single-piece motherboard found in PCs and gaming consoles, each of these three miniaturized boards is designed to be replaced to upgrade the PISTON in the future."
Original story: “We believe, and I think the market’s very clear about this, that the biggest concentration today is in the Windows marketplace,” Xi3 CMO David Politis told PC Gamer.
“We’re still friends. We still love Valve, we love Steam," he added.
"We’ve gone separate directions today - that doesn’t mean we’re not supporting Valve. They’ve got 50+ million users on Steam. Why wouldn’t you support them?
"But the thing is, so does EA, with Origin. So we support Origin as well. In fact, we believe that if you can play it on a computer you should be able to play it on a Piston - and that’s our whole viewpoint.”
Xi3's Piston was one of the first systems to be announced when Valve began making public forays into hardware at CES 2013, but the two companies parted ways just a few months later, even though Xi3 said Valve has specifically commissioned the system.
Xi3 forged on regardless, and the Piston was released in November for $999. It isn't modular, so users can't upgrade components, but it does allow for Linux installs as well as Windows and a custom environment.
When Valve's hardware plans resurfaced, the company had distanced itself from the "SteamBox" name, opting for Steam Machines. Its new plan involved multiple manufacturers creating systems compatible with SteamOS, a custom, Linux-based operating system.