Apparatus and method for implementation of a page frame replacement algorithm in a data processing system having virtual memory addressing

摘要

In a multiprocessor, multiprogrammed data processing system employing virtual addressing, apparatus and method are provided for selecting a page frame in a main memory unit to be replaced by a new page frame of logic signal groups required by a processor. Rather than utilize an algorithm implemented in a series of logical decisions determined by a software procedure, the present invention provides for a single instruction that uses the status signals included with a page descriptor to address an entry in a table of resulting status signals. The relationship between the status signals and the table entries implements the algorithm. The table with entries of resulting status signals is associated with the instruction and is stored in the processor when the instruction is prepared for execution by the processor. The resulting status signals are stored with the page descriptor, replacing the original status signals. The resulting status signals are analyzed by a software procedure, the software procedure implementing the page replacement activity and executing other activity indicated by the resulting status signals.