OSNews

Laurence,

"I might be saying something really stupid here, so please forgive me; but if the existing architecture has drivers written in a modular / self-contained way, then wouldn't that be a hybrid kernel?"

Oh I see what you are thinking. Instead of explaining it in my own words, I'll drop a fairly decent wikipedia article on the matter:

https://en.wikipedia.org/wiki/Monolithic_kernel

"A monolithic kernel is an operating system architecture where the entire operating system is working in the kernel space and alone as supervisor mode."

and
"Modular operating systems such as OS-9 and most modern monolithic operating systems such as OpenVMS, Linux, BSD, and UNIX variants such as SunOS, and AIX, in addition to MULTICS, can dynamically load (and unload) executable modules at runtime. This modularity of the operating system is at the binary (image) level and not at the architecture level. Modular monolithic operating systems are not to be confused with the architectural level of modularity inherent in Server-Client operating systems (and its derivatives sometimes marketed as hybrid kernel) which use microkernels and servers (not to be mistaken for modules or daemons)."


In short, a hybrid or microkernel differs in that it uses the CPU segregation mechanisms to protect pieces of the kernel from itself. This typically has further implications, like microkernel modules needing to communicate via IPC instead of being able to hook into each other more directly via dynamic linking or function pointers. But either kernel style could have pluggable modules (similar to DLLs).