Thayne C Cooper

US Patent:

50776576, Dec 31, 1991

Filed:

Jun 15, 1989

Appl. No.:

7/367271

Inventors:

Thayne C. Cooper - West Valley City UT
Wayne D. Bell - Bountiful UT

Assignee:

Unisys - Blue Bell PA

International Classification:

G06F 906
G06F 1206
G06F 124

US Classification:

395500

Abstract:

An emulator is comprised of a host processor, an emulator, assist unit, and a memory which are closely coupled together over a co-processor bus. Stored in the memory is a user program which is a sequence of instructions from a user instruction set that is to be emulated, and a control program which is a mixture of host processor instructions and emulator assist unit instructions. In operation, the host processor reads and executes the hosts instructions, and it reads and passes the emulator assist unit instructions to the emulator assist unit for execution in that unit. By this means, the host processor and the emulator assist unit share the emulation tasks; and those tasks which are most difficult for the host are performed by the emulation assist unit. As one example the emulator assist unit has registers and controls which respond to the emulator assist unit instructions by examining the fields of the next user instruction that is to be emulated and by generating memory addresses of the operands which that next user instruction operates on; while the host uses those addresses to read the operands from memory and perform operations on the operands as specified by the user instruction.