Pipeline del procesador Rock de Sun

Un pipeline con un nuevo sistema predictivo, capaz de suspender hebras bloqueadas. Competencia del procesador Cell de las PS3.

Sun: Can you smell what the Rock is cookin'?

A Rock core's pipeline. Source: Sun

In Sun's new model, instructions enter the front end of the machine, where they're decoded before being dispatched and reordered like normal. But if the instruction stream stalls for a long time while waiting on main memory to load data, Rock first saves the thread's state in a "checkpoint" and then launches a "scout thread" that runs ahead of the (now stalled and saved) main thread. This scout thread (ST) is a hardware entity that's totally invisible to the operating system, hypervisor, or whatever else has control of the processor, and in the course of execution it predicts and resolves branches, prefetches code and data, and saves its speculative state in a shadow register file. Most importantly, the scout thread can actually retire some of the instructions that it speculatively executes.