Method and means for switching system control of CPUs

Details Method and means for switching system control of CPUs Method and means for switching system control of CPUs

1982-04-26

1985-01-15

Heckler, Thomas M.

Boots, shoes, and leggings

G06F 910

Patent

active

044941897

ABSTRACT:
The embodiment obtains rapid switching between system control programs (SCPs) by switching an address in a prefix register in a CPU of a MP or UP data processing system from a guest SCP's PSA (program save area) to a host SCP's PSA by fetching the host prefix value from a predetermined control block in main storage. The prefix register loading changes the control of the CPU from a preferred guest SCP to a host SCP. This SCP switching is done by hardware and/or microcode means in the CPU. It further detects preset states in the CPU that enable a rapid determination of which SCP is to handle a sensed event, permitting the guest SCP to immediately handle events predetermined to belong to the guest. This manner of CPU control obtains for a preferred guest SCP (such as MVS/370) operating under a host SCP (such as VM/370) nearly the efficiency of standalone execution on the CPU by the preferred guest SCP.

REFERENCES:
patent: 4042912 (1977-08-01), Bachman et al.

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