NASM 2.05 based x86 Instruction Reference[ch207]
A.5.184 MUL: Unsigned Integer Multiply MUL r/m8 ; F6 /4 [8086] MUL r/m16 ; o16 F7 /4 [8086] MUL r/m32 ; o32 F7 /4 [386] MUL performs unsigned integer multiplication. The other operand to the multiplication, and the destination operand, are implicit, in the following way: - For MUL r/m8, AL is multiplied by the given operand; the product is stored in AX. - For MUL r/m16, AX is multiplied by the given operand; the product is stored in DX:AX. - For MUL r/m32, EAX is multiplied by the given operand; the product is stored in EDX:EAX. Signed integer multiplication is performed by the IMUL instruction: see section A.5.118.