The wait is (almost) over. On Friday, Valve will start shipping its Steam machines prototypes and controllers to 300 beta participants.

Valve started notifying those who had been selected to receive the hardware at 5 p.m. ET today. Once the machines leave the factory later this week, the SteamOS will be activated and available for download only in America by individual users and commercial OEMs.

The beta is limited to the U.S. “because of regulatory hurdles,” Valve designer Greg Coomer wrote in a blog post(Opens in a new window).

That means there will be no feedback from international customers, “which is pretty unfortunate,” he said, but “all things considered, we’re sure it was the right decision, because the alternative was to delay the whole beta beyond the point when we’d be able to incorporate any feedback into the 2014 products.”

Those 300 prototype units will come equipped with either an Intel Core i7-4770, Core i5-4570, or an unspecified Core i3.

Valve’s Coomer almost promised that an in-home streaming beta will begin soon.

At this point, the prototype will be the only Steam Machine that Valve will actually produce. The company will focus on SteamOS, while third-party manufacturers – like iBuyPower – will make the Steam Machines that consumers can actually buy. More details about those devices are expected at CES next month from companies like Digital Storm, which will reveal the first liquid-cooled Steam Machine(Opens in a new window) at the show.

Focused on graphics, Digital Storm’s new small form factor system boasts best-in-class performance, a full-sized liquid cooling solution, up to a 700-watt power supply, and advanced airflow thermal management. With access to SteamOS and Windows, users can play any PC game on their big screen — for a hefty price. Digital Storm’s machine will start at $1,469, with configurations that can handle a Nvidia GeForce GTX Titan graphics card.

The Steam Machine prototype launch comes as the gaming platform announced a milestone 7.19 million concurrent online users — a first for the popular site, and a reminder the PC-based gaming is still very much alive.

For more, see Valve Steam Machines, Steam Controller, and SteamOS: Visionary or Vapor?