
740 CHAPTER 9 Hardware/Software Trade-Offs
when they are otherwise idle (or to develop early versions of parallel applications).
At least in the short term, economic reasons might nonetheless provide all-software
solutions with another role. Since vendors are likely to build tightly coupled systems
with only a few tens or a hundred nodes, connecting these hardware-coherent
systems together with a software coherence layer may be the most viable way to con-
struct very large machines that still support the coherent shared address space
programming model. While supporting this programming model on scalable sys-
tems with physically distributed memor ...