When doing an operation like mov [eax], ebx you are able to use simple arithmetics on the value in the brackets. Like mov [eax+10], ebx or mov [eax*8], ebx.
When using addition you don't really have limitation what number to add. But when using multiplication you can only can use 1,2,4,8, at least that's what I thought.
But operations like this: mov [eax*3], ebx or this: mov [eax*9], ebx seem to be valid. Other operations like: mov [eax*6], ebx or mov [eax*7] are invalid. 
So, does anyone has an explanation for this?
 
    