Apparatus and method for emulation routine pointer prefetch

Details Apparatus and method for emulation routine pointer prefetch Apparatus and method for emulation routine pointer prefetch

1993-09-20

1996-11-12

Teska, Kevin J.

Boots, shoes, and leggings

395800, 395376, 364DIG1, G06F 300, H01J 900

Patent

active

055748872

ABSTRACT:
An apparatus and method for emulation routine pointer prefetch are disclosed. The apparatus includes an emulated program counter (EPC), a prefetch state machine, a summing device, an opcode storage device, and a pointer storage device. The EPC, opcode storage device and pointer storage device are coupled to a bus to receive, store and output an emulated program counter value, an opcode value and a pointer to a next emulation routine. The EPC, opcode storage device, and pointer storage device are controlled by the prefetch state machine, which also is coupled to the bus to detect a reference to a reserved memory address and stores an updated emulated program counter value in the EPC using the summing device. The prefetch state machine uses the EPC value to prefetch the next source instruction to be emulated in a first memory operation. A portion of the prefetched source instruction is the opcode value and is stored in the opcode storage device. The prefetch state machine uses the opcode value in a second memory operation to retrieve a pointer to a corresponding emulation routine which is stored in the pointer storage device. The method for emulation routine pointer prefetch preferably comprises the steps of determining if a currently executing emulation routine has issued an instruction to update the EPC; prefetching a next source instruction based upon the value of the EPC; and using an opcode within the prefetched source instruction to prefetch a pointer to a next emulation routine corresponding to the prefetched source instruction.

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