Evolving Operating Systems and Architectures: How Do Kernel Implementors Catch Up?

Introduction Computer architectures have evolutionary changes as the hardware technology advances. For example, the intel 80x86 family of microprocessors have evolved from x = 1 to x = 4 and onward. Although each of these microprocessors is "upward-compatible" with its predecessor, a naive port of the operating system (OS) kernel implemented for the predecessor does not run well on the successor. Even though many of the differences are "transparent" to the programmer, e.g., the different bus widths and on-chip cache sizes, they have profound impact on the performance of different kernel routines. Typically, the OS kernel is rewritten for the new member of the family, despite the instruction set compatibility. In addition, sometimes computer architectures have intentionally very distinct external interfaces and internal designs. For example, there are several competing architectures based on the RISC technology, such as SPARC, HP-PA, and