CPU slot(s) and/or socket(s)

The type of CPU slot or socket determines which processors the motherboard can use. The most popular CPU connectors are Socket 370 (late-model Intel Pentium III and Celeron processors), Socket A (AMD Athlon and Duron), Socket 478 (current Celeron and Pentium 4), Socket 423 (old-style Pentium 4), Slot 1 (old-style Pentium II/III and Celeron), Slot A (older-style Athlon), and the obsolete Socket 7 (Intel Pentium and AMD K6-* processors). Some motherboards have two or more CPU connectors, allowing them to support multiple processors. A few motherboards have both Slot 1 and Socket 370 connectors, allowing them to support either type of CPU (but not both at once).

There are three versions of Socket 370, which differ in pinouts and which processors they support. Early Socket 370/PPGA motherboards support only older Mendocino-core Celeron processors. Later Socket 370/FC-PGA motherboards support Coppermine-core Pentium III FC-PGA processors and Coppermine128-core Celeron FC-PGA processors. The final Socket 370 motherboards, which Intel refers to as "Universal" models, support any Socket 370 processor, including Tualatin-core Pentium III and Celeron processors. Although Socket 370 is now obsolescent, tens of millions of Socket 370 systems remain in use. When you upgrade such a system it is important to check the documentation to determine which Socket 370 variant that system uses.