20
Networks (continued)
•Direct
Networks
–Short,
nearest neighbor paths are available
–Adaptive
routing techniques are available
–Much
more asynchronous; NIC is extra processor
–Different
load properties for different architectures
•Non-shared
memory, network carries little overhead
•Shared
memory, network carries coherency protocol messages, which can be “proportional to
the sharing”
–n-ary,
d-cubes are realistic topologies
•Torus
is better because of symmetry
•Fat
trees also work; hypercube has “log P node degree”
Direct (regular) networks are only
choice