Found this set of slides particularly informative on XEN and TPM.
Thought they might be useful for the less techie folks who hate to slog through the jargon and incomprehensibility of most of the pdfs. Note that many of the diagrams seem to be direct decendants of diagrams AWK posted here long ago about issues that needed to be solved.
Note especially, pages 6, 26, and the ubiquitous comment on 33 particularly
Market Data 
Markets 
AI
