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M. Perner, U. Schmid, C. Lenzen, M. Sigl:
"Byzantine Self-Stabilizing Clock Distribution with HEX: Implementation, Simulation, Clock Multiplication";
Talk: DEPEND 2013, The Sixth International Conference on Dependability, Barcelona, Spain; 2013-08-25 - 2013-08-31; in: "Proceedings of the 6th IARA International Conference on Dependability (DEPEND'13)", IARA, (2013), ISBN: 978-1-61208-301-8; 6 - 15.

We present a prototype implementation and simu\-lation-based evaluation of a
recently proposed novel approach for Byzantine fault-tolerant and self-stabilizing clock distribution in multi-synchronous
GALS architectures. Fault-tolerant clock generation and clock distribution
is a mandatory prerequisite for highly dependable
multicore processors and Systems-on-Chip, as it removes the single
point of failure typically created by central oscillators and conventional
clock distribution trees.
Our scheme, termed HEX, is based on a hexagonal grid topology, which connects
simple intermediate nodes implemented using the UMC 90~nm standard cell library.
Their purpose is to (i) forward synchronized clock signals throughout the grid
and (ii) to supply the clock to nearby application modules. To achieve (ii), we
show how to construct a \emph{fast clock} on top of the clock signal provided by
HEX and analyze its properties. In sharp contrast to existing solutions, HEX is
not only Byzantine fault-tolerant, but also self-stabilizing, i.e., it can
recover from arbitrarily corrupted system states. ModelSim-based simulation
experiments confirm the excellent performance and fault-tolerance properties of
our approach achieved in practice, which were already suggested by an earlier
theoretical worst-case analysis.

fault-tolerance; self-stabilization; clock distribution; fault-injection; simulation analysis