supercomputers have typically used sparse interconnect topologies like Star, Ring, Torus (e.g. IBM’s Blue Gene/L), or hypercube (Cray). These are more scalable as far as building the interconnect for really large numbers of nodes is concerned. However, the downside is that nodes are not directly connected to each other and messages have to go through multiple hops before reaching the destination. Here, unless the applications are designed very carefully to reduce message exchanges between different nodes (especially those that are not directly connected to each other), the interconnect becomes a bottleneck for application scaling.
In contrast to those systems, Eka uses an interconnect designed using concepts from projective geometry. The details of the interconnect are beyond the scope of this article. (Translation: I did not understand the really complex mathematics that goes on in those papers. Suffice it to say that before they are done, fairly obscure branches of mathematics get involved. However, one of these days, I am hoping to write a fun little article on how a cute little mathematical concept called Perfect Difference Sets (first described in 1938) plays an important role in designing supercomputer interconnects over 50 years later. Motivated readers are encouraged to try and see the connection.)
To simplify – Eka uses an interconnect based on Projective Geometry concepts. This interconnect gives linear speedup for applications but the complexity of building the interconnect increases only near-linearly.