It's in the nature of a fast-moving field like computer architecture that sources become out of date quickly. It's easy to think of obsolescent and failed designs as being only of historical interest. While they do have historical interest, they can also provide valuable insight in helping understand the design space. Thus this page collects some interesting examples - forgive me if the links are sometimes dead.
Also of interest: check out "Missing the memory wall..." - on integrating the CPU and the DRAM on the same chip.
The most important tool for studying issues in computer architecture is a simulator. It's boring to write one's own - but fortunately there are some good ones available freely on the web. Here's a selection: