IBM Power5: A Short History
A brief look at what the IBM POWER5 processor and the eServer i5/p5 lines were, and why they matter today mainly as the starting point of a migration decision.
This site is built around a migration decision, not a history lesson, so we keep this part short. If you're here to research what Power5 actually was, here's the essential background.
POWER5: released 2004
IBM's POWER5 processor debuted in 2004 as the successor to POWER4, introducing simultaneous multithreading and Micro-Partitioning, the ability to divide a single physical processor into multiple logical partitions at sub-whole-processor granularity. It shipped in two parallel IBM product lines: the eServer i5 for IBM i (then i5/OS) workloads, and the eServer p5 for AIX and Linux. IBM renamed these the System i and System p brands in 2006.
What it replaced, and what replaced it
POWER5 succeeded POWER4-based iSeries and pSeries hardware. It was, in turn, succeeded by POWER6 in 2007, the generation on which System i and System p were unified into a single Power Systems brand in April 2008, ending the separate iSeries/pSeries hardware lines Power5 was part of.
For the technical specifics of your exact machine, see our model directory. For what running this hardware means today, see our end-of-support and migration pages, that's the part of this site built to actually help.