First of all let’s get the acronyms out of the way:
In my view, both HAM and SAM are components of ITAM.
SAM tends to get more exposure and emphasis (especially on this site) because:
However rather than being separate disciplines I believe there is significant overlap. You can’t really do one without the other. Implementing a good SAM practice will undoubtedly have good repercussions on the management of other assets but will fall short of full ITAM. The key dependency between HAM and SAM is the platform – which is usually very important. It could be firmware on a switch, the number of processors on a server or the operating system of a desktop.