More on Intel Arithmetic and Logic Operations (2006)

by Norman Matloff.

One of the Intel instructions for multiplication is imull (“IMUL long,” i.e. for 32-bit operations). One form of IMUL is imull src where src is a 32-bit multiplier specified in register mode. The multiplicand is implicitly EAX, and the product is stored in what is described in Intel literature as EDX:EAX. To see what this means, note that when we multiply two 32-bit quantities, we potentially get a 64-bit product. So, the Intel hardware places the upper 32 bits in EDX and the lower 32 bits in EAX. [via]

http://heather.cs.ucdavis.edu/~matloff/50/PLN...