Patent ID: 7802252

Claim:
A method for selecting in real-time an architecture level to which a processor appears to conform, said method comprising: setting a value of one or more bits within a pre-assigned processor compatibility register (PCR) within the processor, said value of said pre-assigned PCR identifying an architecture level to which the processor is to conform from the perspective of a logical partition or program during subsequent execution of the logical partition or program on the processor; wherein the value of the one or more bits within the pre-assigned PCR identifies the architecture level desired for proper execution of the logical partition or program, whose pending execution triggers the setting in real-time of the value of the pre-assigned PCR to configure the processor to operate according to the identified architecture level from among multiple different architecture levels to which the single processor can be configured to conform, wherein each of the multiple different architecture levels is identified by a different value of the one or more bits within the PCR and wherein proper execution of the logical partition or program is not fully supported when the processor operates in a different architecture level from the identified architecture level; and when the processor is not currently configured to operate at the identified architecture level, automatically configuring the processor to conform to the identified architecture level, that corresponds to the value of the one or more bits within the pre-assigned PCR, wherein said automatically configuring re-configures the processor for operation as a newer architecture level processor or an older architecture level processor desired for proper operation of the logical partition or program, based on the value of the bits within the pre-assigned PCR.