K42 is an open-source research operating system for cache-coherent 64-bit multiprocessor systems. It was developed primarily at IBM Thomas J. Watson Research Center in collaboration with University of Toronto and University of New Mexico. The main focus of this OS is to address performance and scalability issues of system software on large-scale, shared memory, NUMA multiprocessor computers.
K42 utilizes a microkernel architecture rather than the traditional monolithic kernel design. K42 consists of a small exception-handling component that serves as the microkernel, a fast IPC mechanism called protected procedure call (PPC), and servers for most other components of the operating system. These servers exist in separate address spaces and rely upon the fast IPC mechanism for communication with the microkernel and other servers.
The core of K42 is based on the University of Toronto's Tornado Operating System. K42 is the university's third generation of research on scalable operating systems. Tornado OS / NUMAchine Multiprocessor was the second generation and Hurricane OS / Hector Multiprocessor was the first generation.
K42 currently supports the Linux PPC64 and PPC32 ABIs, so most PowerPC Linux binaries can run on K42 without modification, including the DB2 relational database. K42 has some device drivers implemented specifically for it, but it gets most of its hardware support by directly linking in Linux device drivers to a special server.
Another goal of the K42 design is to achieve a customizable and maintainable system. Being built with an object-oriented design, it allows applications to customize and thus optimize the OS services required, and then on the fly hot swap kernel object implementations. This is particularly important for applications, such as databases and web servers, where the ability to control physical resources can improve performance.
Open Source 
The K42 source is available via the git command:
git clone http://silicoinformatics.seas.harvard.edu/kitchsrc.git