A shared-memory multiprocessor system using the raw tiled architecture

Abstract

Recent trends in microprocessor design have moved away from dedicated hardware mechanisms to exposed architectures in which basic functionality is implemented in software. To demonstrate the flexibility of this scheme, I implement a shared memory system on Raw, a tiled multiprocessor. A traditional directory-based cache coherence system is used. The directories are fully resident on several tiles, and the remaining tiles act as users, with cache maintenance routines accessed via interrupt. Previous implementations of shared-memory systems have mostly relied on a combination of dedicated hardware and user-enabled software hooks, with one notable exception, Alewife, combining basic hardware with software support for corner cases. Here, the focus is moved to placing as much support for basic cases into software as possible. The system is designed to minimise custom hardware and user responsibilities. I prove the feasibility of such a design on an exposed architecture such as Raw.