Compact gaming machines are sold on their processor and graphics chip, but the figure that predicts how one behaves is the chassis volume in litres. Heat has to get out, and the smaller the box the harder that becomes, so a chip permitted 130W in a fifteen-litre case may be configured for half of that in a four-litre one while wearing exactly the same name on the sticker. Reading the litres first tells you which class of machine you are looking at.

There are roughly three of those classes. At about a litre a machine runs on integrated graphics alone, which suits esports titles, emulation and older libraries. Between three and five litres it can carry a laptop-class discrete chip and handle current releases at 1080p. From around eight litres upwards a mini-ITX build accepts a full desktop graphics card, and at that point raw performance stops being the compromise and physical clearance becomes the thing that decides the build.