I dug up a bunch of links for Soccerman recently...
Start with the articles at
Ace's Hardware (The Secrets of High Performance CPUs series is a good start) and at
Ars Technica.
Once you're feeling brave, move on to course notes for
CS 552 (Comp Arch),
CS 752 (Advanced Comp Arch), and
CS 757 (Parallel Processing) (I can't guarantee how readable these are, since they're supposed to supplement the classes and not replace them). Also check out
Paul DeMone's Silicon Insider articles at Real World Tech (the forums there are excellent). If you're feeling really courageous, I recommend getting a copy (from a library if possible, they're expensive) of
Computer Organization and Design (the undergrad version) or
Computer Architecture (the graduate version) by Hennessey and Patterson....
Computer Architecture is widely regarded as the Bible in the field, brought to you by the guys who first advocated the RISC model of computing, and whose work at Stanford and Berkeley, respectively, spawned the SPARC and MIPS architectures.
Computer Architecture is the kind of subject in which you can do a lot of hand-waving to give a general impression of the field, but I really recommend a college-level textbook (and a thorough set of coursework in CS/CE and Comp Arch

) to get a real grasp on how everything really works on the architectural level, as well as the various design trade-offs. While
Computer Organization and Design does have a chapter on basic assembly programming & ISAs as well as a short appendix on digital logic circuits, I can't gauge how well the entire text can be read without previous courses in these subjects.