dunigan@MSR.EPM.ORNL.GOV (Tom Dunigan 576-2522) (02/20/91)
Algorithms for providing internal time and frequency synchronization of the clocks of Intel and Ncube hypercube multiprocessors are presented in the tech. report "Hypercube Clock Synchronization", ORNL/TM-11744. Bounds for the error in estimating clock offsets and frequency are formulated in terms of the clock read error and message transmission time. The report describes clock and communication performance of the Ncube and Intel hypercubes and performance of the synchronization algorithms. Internal synchronization within 10s of microseconds can be achieved. The following is a summary of the clock characteristics of the Intel and Ncube hypercubes. Hypercube Clock Parameters iPSC/860 iPSC/2 N6400 N3200 Crystal frequency (MHz) 40 20 80 32 Measured frequency difference (ppm) 80 25 0 0 Clock precision (us) 0.1 1.0 0.05 128 Effective clock precision (us) 1 15 1 128 Clock read error (us) 60@10ms 260@50ms 30@20ms 128 Round-trip error (d6) (us) 120 527 60 128 Filtered round-trip error (d6) (us) 25 114 18 128 Minimum message time (us) 64 302 151 511 Monotonic clock yes no yes no Ncube hypercube node processors share a single clock source. No time or frequency synchronization is required for the Ncube 6400. The Ncube 3200 uses a software clock, initial time synchronization is required. Intel hypercube node processors each have their own crystal, both time and frequency synchronization are required, including periodic re-synchronization.