Volume 3: General-Purpose and System Instructions - Stanford ...

24594 Rev. 3.10 February 2005 AMD64 TechnologyMnemonic and any operands Opcode Description of operation24594 Rev. 3.07 September 2003 AMD64 TechnologyAAMASCII Adjust After MultiplyConverts the value in the AL register from binary to two unpacked BCD digits in theAH (most significant) and AL (least significant) registers using the following formula:AH = (AL/10d)AL = (AL mod 10d).In most modern assemblers, the AAM instruction adjusts to base-10 values. However,by coding the instruction directly in binary, it can adjust to any base specified by theimmediate byte value (ib) suffixed onto the D4h opcode. For example, code D408h foroctal, D40Ah for decimal, and D40Ch for duodecimal (base 12).Using this instruction in 64-bit mode generates an invalid-opcode exception.Mnemonic Opcode DescriptionAAM D4 0A Create a pair of unpacked BCD values in AH and AL.(Invalid in 64-bit mode.)(None) D4 ib Create a pair of unpacked values to the immediate byte base.(Invalid in 64-bit mode.)Related InstructionsAAA, AAD, AASrFLAGS AffectedID VIP VIF AC VM RF NT IOPL OF DF IF TF SF ZF AF PF CFU M M U M U21 20 19 18 17 16 14 13–12 11 10 9 8 7 6 4 2 0Note: Bits 31–22, 15, 5, 3, and 1 are reserved. A flag set to 1 or cleared to 0 is M. Unaffected flags are blank. Undefined flags are U.ExceptionsException RealVirtual8086 Protected Cause of ExceptionDivide by zero, #DE X X X 8-bit immediate value was 0.Invalid opcode, #UD X This instruction was executed in 64-bit mode.“M” means the flag is either set orcleared, depending on the result.AAM 63Possible exceptionsand causes, by modeof operation“Protected” columncovers both legacyand long modeAlphabetic mnemonic locatorFigure 2-1.Format of Instruction-Detail PagesChapter 2: Instruction Overview 29