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To anyone using the current Ubuntu image 4/4 - Dosbox runs at an amazing 60fps. I've gotten all the classic titles to work, requires some emulator knowledge. I even got WarCraft II working very well. However if you'd like a copy of my dosbox.conf, lemme know and I'll pastebin it.
Performance tips : Run it on "surface", no opengl. Use 640x520 fullscreen for games like Warcraft or Settlers II.
Turn off compositing (xfce, compton, xcompmgr). Use a lightweight window manager (i recommend i3 for the board, performs very well).
xrandr -s 0
xrandr -s 1
xrandr -s 2
*these commands will change monitor resolution on the fly
Also, Clementine, the internet radio client, works too - you can stream spotify with a premium account. Happy computing!