Ask YC : x86 books?

I have just started a compiler project targeting x86. Can you suggest some books which will get me upto speed on the the x86 instruction set? I have worked with other ISAs in the past so I am not an assembler noob. Just want something to teach me x86. A book which gives an overview of newer intel chips (intel core microarchitecture?) will also be helpful.

edit : I also need to understand the SSE instructions since the compiler is expected to do some vectorization.