Istvan Nagy 
Complex Digital Hardware Design [PDF ebook] 

This book is about how to design the most complex types of digital circuit boards used inside servers, routers and other equipment, from high-level system architecture down to the low-level signal integrity concepts. It explains common structures and subsystems that can be expanded into new designs in different markets.The book is targeted at all levels of hardware engineers. There are shorter, lower-level introductions to every topic, while the book also takes the reader all they way to the most complex and most advanced topics of digital circuit design, layout design, analysis, and hardware architecture.