Once the kernel loads and hands off the boot process to the init command, the same sequence of events occurs on every architecture. So the main difference between each architecture's boot process is in the application used to find and load the kernel.

For example, the Itanium architecture uses the ELILO boot loader, the IBM eServer pSeries architecture uses YABOOT, and the IBM eServer zSeries and IBM S/390 systems use the z/IPL boot loader.

Consult the Red Hat Enterprise Linux Installation Guide specific to these platforms for information on configuring their boot loaders.