Just a quicky...
I am learning AT&T x86-64 assembly syntax and boy how different Intel and AT&T are.
At least there are similarities between AT&T and Motorola 68K syntax the way they are laid out so that does make it a little easier.
I have all the Manuals for the Intel Instruction Set and Applications thereof from Intel themselves, a free download set from about 4 years ago, but I can't find the equivalent for AT&T format.
There is this though so seems like a good alternative and will at least put me on the right track: