Red Hat Enterprise Linux 5.4 adds support for processor degradation, which allows processor speed to be reduced in some circumstances (i.e. system overheating). This new feature allows automation software to observe the machine state and act based on defined policies.
Processor degradation is supported on z990, z890 and later systems and is observed through SCLP system service event type 4 event qualifier 3. STSI will report the new capacity of the processor in the file: <filename>/sys/devices/system/cpu/cpuN/capability</filename>.