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Interconnection structures in multiprocessing

Short answer

Common bus is simple but limited; multiport memory allows several simultaneous accesses at high cost; crossbar provides non-blocking but is expensive; multistage networks offer scalable switching with possible blocking; hypercubes use direct links between neighbors for efficient routing.

Compare and contrast the interconnection structures used in multiprocessing environment.

The processors, memory modules and I/O in a multiprocessor are connected by the following structures:

  1. Time-shared common bus: one bus is shared by all modules; only one transfer at a time.
  2. Multiport memory: each memory module has several ports, one per processor; priority resolves conflicts.
  3. Crossbar switch: a switch at each crosspoint between processors and memory modules; many simultaneous transfers.
  4. Multistage switching network: stages of 2×2 switches (omega network) between processors and memories.
  5. Hypercube: 2ⁿ processors, each connected to n neighbours, differing by one address bit.
PointCommon busMultiport memoryCrossbarMultistageHypercube
Simultaneous transfersOneSeveral (per module)MaximumSeveral, with blockingMany links
Cost / hardwareLowestHigh (extra memory ports)Highest, N² crosspointsN/2 · log₂N switchesN · n/2 links
ContentionHighestMemory conflictsOnly at the same memoryPossible path conflictsPossible link conflicts
ScalabilityPoorPoorPoor (cost)GoodGood
ComplexitySimplestMediumComplex controlRouting logicRouting by XOR

✓ Answer checked by Claude Opus 5.5 (high effort)

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