http://opensecuritytraining.info/IntermediateX86.html
Assumes: Intro x86
Teaches: x86 internals that are used by many OSes or security tools. The exact implementation of privilege rings, protected mode segmentation, regular and Physical Address Extensions (PAE) paging and memory management, interrupts and the Interrupt Descriptor Table(IDT), hardware debug registers, port IO.
Xeno Kovah graduated from the CMU SFS program in 2007 and has been leading a team focusing on sophisticated stealth malware detection (in userspace, kernel, and firmware) and trusted computing at MITRE since 2009. But he's been attending cons since 1999, back before The Shmoo Group had even made a splash at Defcon with their wireless shenanigans. ;) Xeno started OpenSecurityTraining.info in 2011 to host his like-minded colleagues' open source training materials, and he's always looking for new contributors.