A system and technique facilitate fast context switching among processor
complex stages of a pipelined processing engine. Each processor complex
comprises a central processing unit (CPU) core having a plurality of
internal context switchable registers that are connected to respective
registers within CPU cores of the pipelined stages by a processor bus. The
technique enables fast context switching by sharing the context switchable
registers between upstream and downstream CPUs to, inter alia, force
program counters into the downstream registers. In one aspect of the
inventive technique, the system automatically reflects (shadows) the
contents of an upstream CPU's context switchable registers at respective
registers of a downstream CPU over the processor bus. In another aspect of
the invention, the system redirects instruction execution by the
downstream CPU to an appropriate routine based on processing performed by
the upstream CPU.