[dekhn]

Many clusters have tight interconnect, yet I don't call them supercomputers.

Supercomputers are more defined by their capabilities and max capacities: they tend to be orders of magnitude larger in their max memory, and their ability to do X, Y, or Z. It's really just a term at this point, not something truly differentiating.

[metaobject]

I agree. We have a 128 node cluster where I work (that has infiniband interconnect, etc), but I wouldn't call it a supercomputer. Some of my colleagues, however, have access to machines at various national labs (ORNL, e.g.) that I would call supercomputers. I suppose it's all relative, though. For someone who's only ever developed on a dual-core 2 GHz machine, a 128 multi-core node cluster might be considered the equivalent of The WOPR.

[alephnil]

I agree that a 128-node computer would not be called a supercomputer regardless of interconnection, my point was more the other way, that a computer without fast interconnections would still be called a cluster, and not a supercomputer regardless of the number of nodes.