OPCODE MAP

B.5 ESCAPE OPCODE INSTRUCTIONS

Opcode maps for coprocessor escape instruction opcodes (x87 floating-point instruction opcodes) are in Table B-7 through Table B-22. These maps are grouped by the first byte of the opcode, from D8-DF. Each of these opcodes has a ModR/M byte. If the ModR/M byte is within the range of 00H-BFH, bits 3-5 of the ModR/M byte are used as an opcode extension, similar to the technique used for 1-and 2-byte opcodes (see B.4). If the ModR/M byte is outside the range of 00H through BFH, the entire ModR/M byte is used as an opcode extension.

B.5.1 Opcode Look-up Examples for Escape Instruction Opcodes

Examples are provided below.

Example B-6. Opcode with ModR/M Byte in the 00H through BFH Range

DD0504000000H can be interpreted as follows:

•The instruction encoded with this opcode can be located in Section . Since the ModR/M byte (05H) is within the 00H through BFH range, bits 3 through 5 (000) of this byte indicate the opcode for an FLD double-real instruction (see Table B-9).

•The double-real value to be loaded is at 00000004H (the 32-bit displacement that follows and belongs to this opcode).

Example B-7. Opcode with ModR/M Byte outside the 00H through BFH Range

D8C1H can be interpreted as follows:

•This example illustrates an opcode with a ModR/M byte outside the range of 00H through BFH. The instruction can be located in Section B.4.

•In Table B-8, the ModR/M byte C1H indicates row C, column 1 (the FADD instruction using ST(0), ST(1) as operands).

B.5.2 Escape Opcode Instruction Tables

Tables are listed below.

OPCODE MAP

B.5.2.1 Escape Opcodes with D8 as First Byte

Table B-7 and B-8 contain maps for the escape instruction opcodes that begin with D8H. Table B-7 shows the map if the ModR/M byte is in the range of 00H-BFH. Here, the value of bits 3-5 (the nnn field in Figure B-1) selects the instruction.

Table B-7. D8 Opcode Map When ModR/M Byte is Within 00H to BFH *

nnn Field of ModR/M Byte (refer to Figure B.4)

NOTES:

*All blanks in all opcode maps are reserved and must not be used. Do not depend on the operation of undefined or reserved locations.

Table B-8 shows the map if the ModR/M byte is outside the range of 00H-BFH. Here, the first digit of the ModR/M byte selects the table row and the second digit selects the column.

Table B-8. D8 Opcode Map When ModR/M Byte is Outside 00H to BFH *

NOTES:

*All blanks in all opcode maps are reserved and must not be used. Do not depend on the operation of undefined or reserved locations.

OPCODE MAP

B.5.2.2 Escape Opcodes with D9 as First Byte

Table B-9 and B-10 contain maps for escape instruction opcodes that begin with D9H. Table B-9 shows the map if the ModR/M byte is in the range of 00H-BFH. Here, the value of bits 3-5 (the nnn field in Figure B-1) selects the instruction.

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Table B-9. D9 Opcode Map When ModR/M Byte is Within 00H to BFH *

nnn Field of ModR/M Byte

NOTES:

*All blanks in all opcode maps are reserved and must not be used. Do not depend on the operation of undefined or reserved locations.

Table B-10 shows the map if the ModR/M byte is outside the range of 00H-BFH. Here, the first digit of the ModR/M byte selects the table row and the second digit selects the column.

Table B-10. D9 Opcode Map When ModR/M Byte is Outside 00H to BFH *

NOTES:

*All blanks in all opcode maps are reserved and must not be used. Do not depend on the operation of undefined or reserved locations.

OPCODE MAP

B.5.2.3 Escape Opcodes with DA as First Byte

Table B-11 and B-12 contain maps for escape instruction opcodes that begin with DAH. Table B-11 shows the map if the ModR/M byte is in the range of 00H-BFH. Here, the value of bits 3-5 (the nnn field in Figure B-1) selects the instruction.

Table B-11. DA Opcode Map When ModR/M Byte is Within 00H to BFH *

nnn Field of ModR/M Byte

NOTES:

*All blanks in all opcode maps are reserved and must not be used. Do not depend on the operation of undefined or reserved locations.

Table B-11 shows the map if the ModR/M byte is outside the range of 00H-BFH. Here, the first digit of the ModR/M byte selects the table row and the second digit selects the column.

Table B-12. DA Opcode Map When ModR/M Byte is Outside 00H to BFH *

NOTES:

*All blanks in all opcode maps are reserved and must not be used. Do not depend on the operation of undefined or reserved locations.