William Stallings
http://www.ziddu.com/download/6873859/COA6ebyWilliamStallings.pdf.html
Tanenbaum
http://www.ziddu.com/download/6873866/Tanenbaum_StructuredComputerOrganization.pdf.html
Hennessy Patterson
http://www.ziddu.com/download/6873928/COA_Patterson_Hennessy.pdf.html