What Is a Motherboard? A Basic Definition

Motherboard diagram
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1. CPU socket 2. Chipset 3. DIMM/RAM slots
4. PCIe x16 slot 5. PCI x1 slot 6. M.2 connector
7. SATA ports 8. Front panel connectors 9. USB 2. header
10. USB 3.1 Gen1 header 11. USB 3.1 Gen2 header 12. ATX power connector
13. CPU power connector 14. BIOS chips 15. CMOS battery
16. Fan headers 17. Front panel header 18. VRM heatsink
19. COM/Serial header 20. TPM header 21. RGB header

The motherboard is where a PC’s CPU, input/output (I/O) and memory connectors live. Above you’ll find a diagram of a typical motherboard and its corresponding parts.

Note that motherboards vary in appearance and available ports and connectors, and things like fan headers, M.2 connectors and the BIOS battery are found in different places depending on your motherboard.

Most motherboards come in one of three sizes:

  • ATX - Measures 12 x 9.625 inches. This is the standard and biggest. As such, it’s the best choice for features and expansion.
  • Micro-ATX - Measures 9.625 x 9.625 inches.
  • Mini-ITX - Measures 6.75 x 6.75 inches. The smallest option. Used in compact PCs.

This article is part of the Tom's Hardware Glossary.

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Scharon Harding

Scharon Harding has over a decade of experience reporting on technology with a special affinity for gaming peripherals (especially monitors), laptops, and virtual reality. Previously, she covered business technology, including hardware, software, cyber security, cloud, and other IT happenings, at Channelnomics, with bylines at CRN UK.