UMA architectures (cont'd)

Problems with UMA machines:

• Not/hardly scalable
  • Bus-based architectures $\Rightarrow$ saturation
  • Crossbars $\Rightarrow$ too expensive (wiring constraints)
  • Multistage networks $\Rightarrow$ wiring constraints + possibly higher latency (more stages)
• Possible solutions
  • Reduce network traffic by caching
  • Clustering $\Rightarrow$ non-uniform memory latency behaviour (NUMA)