Intel ITANIUM ARCHITECTURE - SOFTWARE DEVELOPERS MANUAL VOLUME 1 REV 2.3 Manual page 1754

PSUBUSB/PSUBUSW—Packed Subtract Unsigned with Saturation
Opcode
0F D8 /r
0F D9 /r
Description
Subtracts the individual unsigned data elements (bytes or words) of the source operand
(second operand) from the individual unsigned data elements of the destination
operand (first operand). (See
exceeds the range for the specified unsigned data type, the result is saturated. The
destination operand musts be an MMX technology register; the source operand can be
either an MMX technology register or a quadword memory location.
Figure 3-21.
mm
mm/m64
mm
The PSUBUSB instruction subtracts the unsigned bytes of the source operand from the
unsigned bytes of the destination operand and stores the results to the destination
operand. When an individual result is less than zero (a negative value), the saturated
unsigned byte value of 00H is written to the destination operand.
The PSUBUSW instruction subtracts the unsigned words of the source operand from the
unsigned words of the destination operand and stores the results to the destination
operand. When an individual result is less than zero (a negative value), the saturated
unsigned word value of 0000H is written to the destination operand.
4:452
Instruction
PSUBUSB mm, mm/m64 Subtract unsigned packed bytes in mm/m64 from
PSUBUSW mm,
mm/m64
Figure
Operation of the PSUBUSB Instruction
PSUBUSB mm, mm/m64
– – –
Description
unsigned packed bytes in mm and saturate.
Subtract unsigned packed words in mm/m64 from
unsigned packed words in mm and saturate.
3-21.) If the result of an individual subtraction
10000000
– – –
11111111
00000000
®
Volume 4: IA-32 Intel MMX™ Technology Instruction Reference
01111111 11111000
– –
00010111 00000111
01101000 11110001
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