Intel ITANIUM ARCHITECTURE - SOFTWARE DEVELOPERS MANUAL VOLUME 1 REV 2.3 Manual page 1324

AAD—ASCII Adjust AX Before Division
Opcode
D5 0A
Description
Adjusts two unpacked BCD digits (the least-significant digit in the AL register and the
most-significant digit in the AH register) so that a division operation performed on the
result will yield a correct unpacked BCD value. The AAD instruction is only useful when
it precedes a DIV instruction that divides (binary division) the adjusted value in the AL
register by an unpacked BCD value.
The AAD instruction sets the value in the AL register to (AL + (10 * AH)), and then
clears the AH register to 00H. The value in the AX register is then equal to the binary
equivalent of the original unpacked two-digit number in registers AH and AL.
Operation
tempAL  AL;
tempAH  AH;
AL  (tempAL + (tempAH  imm8)) AND FFH;
AH  0
The immediate value (imm8) is taken from the second byte of the instruction, which
under normal assembly is 0AH (10 decimal). However, this immediate value can be
changed to produce a different result.
Flags Affected
The SF, ZF, and PF flags are set according to the result; the OF, AF, and CF flags are
undefined.
Additional Itanium System Environment Exceptions
Itanium Reg Faults NaT Register Consumption Abort.
Exceptions (All Operating Modes)
None.
4:22
Instruction Description
AAD ASCII adjust AX before division
Volume 4: Base IA-32 Instruction Reference