Slot 1 refers to the physical and electrical specification for the connector used by some of Intel's microprocessors, including the Pentium Pro, Celeron, Pentium II and the Pentium III. Both single and dual processor configurations were implemented.

The Pentium Pro is a sixth-generation x86 microprocessor developed and manufactured by Intel and introduced on November 1, 1995. It introduced the P6 microarchitecture and was originally intended to replace the original Pentium in a full range of applications. Later, it was reduced to a more narrow role as a server and high-end desktop processor. The Pentium Pro was also used in supercomputers, most notably ASCI Red, which used two Pentium Pro CPUs on each computing nodes and was the first computer to reach over one teraFLOPS in 1996, holding the number one spot in the TOP500 list from 1997 to 2000.