This post is a less interesting follow up to my recent catalogue of girth 6 graphs for keyboard wiring, which give 4-key roll over (4KRO). As explained in my first keyboard and Graph Theory blog post, the idea here is applying these graphs to the design of diode-free computer keyboards where the bipartite matrix becomes a sparse scanning matrix. Using a graph with girth 8 gives 6-key rollover (6KRO), high enough not to be a practical limitation, unless perhaps for stenography? Sadly from a mathematical point of view these are mostly subgraphs of the Tutte Coxetter Graph (aka the Tutte 8 Cage), the unique smallest trivalent graph of girth 8.
