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PC Builds

ATX

The most common desktop motherboard and case size standard, with smaller Micro-ATX and Mini-ITX variants.

ATX ATX is the largest common motherboard size; Micro-ATX and Mini-ITX are smaller variants nested at the same corner, and a case fits its own size and smaller but not larger. ATX (full size) 305 mm, most slots Micro-ATX 244 mm, fewer slots Mini-ITX 170 mm, smallest A case fits its own size and smaller, not larger.

The most common desktop form-factor standard, defining the size and mounting-hole layout of a motherboard (and the cases and power supplies built around it). Full-size ATX boards offer the most expansion slots and connectors; the smaller Micro-ATX and Mini-ITX variants trade some of those slots for a more compact build. Cases are rated for the board sizes they accept, and a case generally fits its own size and smaller — an ATX case usually takes Micro-ATX and Mini-ITX boards too, but not the reverse.

Concrete example

a Mini-ITX board fits an ATX case, but a full ATX board won't fit a Mini-ITX case.

What it means when you're buying

pick the form factor first, since it sets how compact the PC can be and how much room you have to expand later.

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