Maybe it's more than you want, but "Computer Architecture - A Quantitative Approach" from Hennessy and Patterson is a very good reference.
If your main interest is CPU cores even a relatively old version will be enough. From memory recent versions (5 and 6, 6 being the latest) have mostly added content on GPU and data center computing, but the sections on CPU architecture are rather stable.
If your main interest is CPU cores even a relatively old version will be enough. From memory recent versions (5 and 6, 6 being the latest) have mostly added content on GPU and data center computing, but the sections on CPU architecture are rather stable.