Patent ID: 7103754

Claim:
A method for executing a machine instruction in a central processing unit, the method comprising the steps of: fetching a machine instruction for execution, the machine instruction being defined for computer execution according to a computer architecture, the machine instruction comprising an opcode field, an operand base address field and a displacement field containing a displacement value, the displacement field comprising any one of: 1) an unsigned displacement field consisting of only an unsigned portion of a given magnitude, the unsigned portion comprising a most significant bit at one end and a least significant bit at the other end or 2) a signed displacement field consisting of a signed portion contiguous with said unsigned portion, wherein said least significant bit of said unsigned portion is contiguous with said signed portion; obtaining an operand base address from a location specified by the operand base address field; determining if the displacement field is an unsigned displacement field or a signed displacement field; if the displacement field is an unsigned displacement field, arithmetically adding the magnitude of the unsigned portion to the operand base address to determine an address of an operand; if the displacement field is a signed displacement field, concatenating the signed portion with the most significant bit of said unsigned portion to form a signed displacement value wherein the signed portion is a high order portion of said signed displacement value and said unsigned portion is a low order portion of said signed displacement value and algebraically summing the signed displacement value and the operand base address to determine an address of an operand; and performing a function defined by the opcode field, wherein the function uses the operand at the determined address.