What is IBM Power11 Systems compatibility mode?

Solution Unverified - Updated

Environment

  • IBM Power Systems server based on Power 11 processor
  • Operating system based on the Linux kernel

Issue

  • What is IBM Power11 Systems compatibility mode?
  • Is IBM Power11 Systems supported in native mode?

Resolution

  • 'Compatibility mode' simply means that the Power11 processor will act and appear in a mode consistent with an earlier generation processor, typically a POWER10 or Power9.

  • When running Linux on a Power11 system, users will sometimes see that the system is running in a `compatibility mode'. Whether the system runs in native mode or compatibility mode is determined by which kernel is running on the system. On boot, the Linux kernel provides the hypervisor with information on what capabilities it supports (which includes the list of CPU versions it supports). The hypervisor has a list of allowed compatibility modes, which on Power 11 would normally be POWER10 or Power9. The hypervisor then chooses the highest mode that is in both lists.

  • As applied to Red Hat Enterprise Linux, in practical terms this means the following:

    • Power 11 systems are fully supported in POWER 10 compatibility mode starting in RHEL 9.4 kernel and subsequent updates.

      • The Power11 is supported in native mode starting with RHEL 9.6 (5.14.0 kernels).
      • RHEL 9.4 release is fully supported on Power 11 system in POWER10 compatibility mode.

    • Power11 systems are fully supported in POWER10 compatibility mode starting in RHEL 8.10 kernel and subsequent updates.

      • The Power11 is not supported in native mode within the main branch of RHEL 8.x (4.18.0 kernels).
      • RHEL 8.10 release is fully supported on Power 11 system in POWER10 compatibility mode.

    • POWER10 systems are fully supported in native mode starting in RHEL 9.0 (5.14.0 kernels) and RHEL 8.4 onwards (4.18.0 kernels)

SBR
Product(s)
Category
Tags

This solution is part of Red Hat’s fast-track publication program, providing a huge library of solutions that Red Hat engineers have created while supporting our customers. To give you the knowledge you need the instant it becomes available, these articles may be presented in a raw and unedited form.