Steam Machines powered by SteamOS are due to hit stores in the coming months and in order to get the best performance you need to make sure that the GPU inside the machine plays nicely with the new OS.  To that end Phoronix has tested 22 GPUs, 15 NVIDIA ranging from a GTX 460 straight through to a TITAN X and seven AMD cards from an HD 6570 through to the new R9 Fury.  Part of the reason they used less AMD cards in the testing stems from driver issues which prevented some models from functioning properly.  They tested Bioshock Infinite, both Metro 2033 games, CS:GO and one of Josh's favourites, DiRT Showdown.  The performance results may not be what you expect and are worth checking out fully.  As well Phoronix put in cost to performance findings, for budget conscious gamers.

"With Steam Machines set to begin shipping next month and SteamOS beginning to interest more gamers as an alternative to Windows for building a living room gaming PC, in this article I've carried out a twenty-two graphics card comparison with various NVIDIA GeForce and AMD Radeon GPUs while testing them on the Debian Linux-based SteamOS 2.0 "Brewmaster" operating system using a variety of Steam Linux games."

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Graphics Cards