Date: September 29, 2005
If you plan to use an existing HMC with a new Power5 server, be sure the HMC version is 4.5. This is a prerequisite of the current Power5 microcode (SF230_145, August 2005).
The new microcode/HMC versions support concurrent maintenance, or the ability to do most microcode upgrades dynamically, without having to take down partitions.
You can download the HMC update from IBM Fix Central
September 29, 2005