I've remembered to check the cluster monkey feed, and seen http://www.clustermonkey.net/Opinions/the-core-diameter.html
The assumption made here is that every node needs to be able to talk to every other node within the assembly. I think there is a large class of problems where direct long-distance communication is not necessary. E.g. if you're simulating a 3d system with local interactions, where long-range interactions emerge by propagating across computational volume in a wave-like fashion your relativistic limits are only limited to the geometry of the node and its direct neighbors. Further nodes will be reached at next refresh, assuming a relativistic cut-through fabric present in each node, or computation where information is passed implicitly by change of state within adjacent node. Such problem classes on such node geometries have no intrinsic size limit to the number of nodes, since communication is always limited to overlapping light cones of subsystems. Obviously smaller nodes means higher refresh rate, so the system asymptotically converges towards a cellular automaton model, with ~nm sized cells. It is provably impossible to do classical computing faster than this. The time domain is rather ~ps than ~us, and maximally possible refresh rate is some ~100 PHz for ~nm sized cells. Obviously, ability to cool such volumes will limit such high refresh rates, even if the computation is reversible (which probably means it has to be adiabatic, and hence also intrinsically slower). It also seems that spintronics is not extremely fast, and spintronics/photonics/plasmonics is likely to be the modes of computation and communication used in such future systems. _______________________________________________ Beowulf mailing list, [email protected] sponsored by Penguin Computing To change your subscription (digest mode or unsubscribe) visit http://www.beowulf.org/mailman/listinfo/beowulf
