(1) The Intel code name for the Pentium chip. The P5 generation includes the Pentium and Pentium MMX CPUs. See Pentium and microarchitecture.

(2) (p5) A family of Unix-based servers from IBM that are based on IBM's POWER5 CPUs and run under the AIX and Linux operating systems. The p5 is the successor to IBM's pSeries (RS/6000) family. Officially known as the eServer p5, the p5 is IBM's server family for computation-intensive applications.

A Huge Range of POWER
Using IBM's POWER5 CPUs, p5 models were first introduced in 2004 with a wide range of capacities. Single CPU rack mounted Express servers started at 3.25 rPerf with 512MB of memory, all the way to the p5 595, a 64-way system rated up to 306.2 rPerf and 2TB of memory. As a point of comparison, pSeries models available at the time of the p5 introduction offered from 4 rPerf to 46.79 rPerf in performance and from 2 to 256GB of memory. See pSeries, AIX and RS/6000.