You Already Have A SteamOS Machine At Home: Here's How
Don't bother going out and buying a several thousand-dollar Steam Machine, Valve says you already have one at home. Requirements for installing SteamOS on the computer you already have are relatively low – just so long as you've been upgrading over the past couple of years. Installing and customizing SteamOS will require that your computer be wiped out – but once you do that, you'll be ready to roll. In other words: the Steam Machine you have at home isn't going to be your main desktop – it'll need to be a machine you don't use that often.
Your make-it-yourself, DIY, "build your own" Steam Machine will be running SteamOS Beta. The process you'll go through at the point at which this article is published will be basically identical to what you'll do when the full, final version of SteamOS is released. This system works with a base code from Debian 7, code-named Debian Wheezy, and you'll recognize the user interface – it's very similar to Steam's Big Picture Mode.
See: SteamOS 2-years later: why you don't want it
What are the SteamOS Hardware Requirements?
• Processor: Intel or AMD 64-bit capable processor• Memory: 4GB or more RAM• Hard Drive: 500GB or larger disk• Video Card: NVIDIA graphics card OR AMD graphics card (RADEON 8500 and later) OR Intel graphics• Additional: UEFI boot support AND USB port for installation
The following steps come from Valve. We'll be sticking to the default installation here – you can also find the Custom Installation if you want to get all configuration-heavy and do everything your own way.
1. Download the default SteamOS beta installation (same link as Custom Installation).2. Format a 4GB (or larger) USB stick with the FAT32 filesystem, unloading the unzipped contents of SteamOSImage.zip provided in the SteamOS download therein. Partition name should be "SYSRESTORE".3. Insert the System Restore USB stick in your target machine. Boot your machine and tell the BIOS to boot off the stick. (You'll likely use the key F8, F11 or F12 to bring up BIOS when you start up your PC).4. Select the UEFI entry, it may look something like "UEFI: Patriot Memory PMAP". If there is no UEFI entry, you may need to enable UEFI support in your BIOS setup."5. Checkmark "Restore Entire Disk" from the GRUB menu.6. Twiddle your thumbs as your installation completes – after this, your computer will shut down completely. You will have to start it up again manually. From there you'll be good to go!
Inside SteamOS you'll log in with your Steam account and have access to the games that work with SteamOS right out the gate. There should be a number of them – completely dependent on how many games you have purchased that have Linux compatibility. Over the past couple of years Valve has been pushing for Linux compatibility on many big games – so you'll probably find at least a few.