Valve has just released the second major preview version of SteamOS, though it mainly brings undisclosed, under-the-hood changes.

The new version is codenamed “Brewmaster,” and is based on Debian Linux 8.1. This follows the original launch of the Debian 7.1-based “Alchemist” in December 2013. “Although there are a lot of changes under the covers, the overall functionality and experience of brewmaster is the same as alchemist and most of the SteamOS FAQ applies to both releases,” Valve’s announcement says.

Keep in mind that Valve had been steadily improving Alchemist over the last 18 months, and the new preview release is considered to be rough by comparison. Valve has only done limited hardware compatibility testing and is particularly interested in cases where hardware or game support has regressed. There are also some known issues, such as desktop mode failing to work on AMD systems.

For now, it’s not even clear whether Brewmaster will make its way onto the first Steam Machine consoles when they arrive in November. Valve says it’s still figuring out whether to use Brewmaster or stick with Alchemy instead.

In the meantime, tech-savvy users who want to help test the latest version can grab it from Valve’s download site and check the FAQ page for setup instructions. Installing SteamOS will erase everything on the machine, and Valve notes that Alchemy users cannot upgrade to Brewmaster without a full system wipe and reinstall.

Why this matters: Just like last year, a slew of Steam Machines are waiting in the wings on the official debut of SteamOS, presumably hoping not to get caught with yet another delay. The fact that Valve is still debating which version to use is somewhat disconcerting, but hopefully the company can get it together in time for the planned November launch.