Charles H. Recchia

On the radiation-induced soft error performance of hardened sequential elements in advanced bulk CMOS technologies

Test chips built in a 32nm bulk CMOS technology consisting of hardened and non-hardened sequential elements have been exposed to neutrons, protons, alpha-particles and heavy ions. The radiation robustness of two types of circuit-level soft error mitigation techniques has been tested: 1) SEUT (Single Event Upset Tolerant), an interlocked, redundant state technique, and 2) a novel hardening technique referred to as RCC (Reinforcing Charge Collection). This work summarizes the measured soft error rate benefits and design tradeoffs involved in the implemented hardening techniques.

Explaining cache SER anomaly using DUE AVF measurement

We have discovered that processors can experience a super-linear increase in detected unrecoverable errors (DUE) when the write-back L2 cache is doubled in size. This paper explains how an increase in the cache tags Architectural Vulnerability Factor or AVF caused such a super-linear increase in the DUE rate. AVF expresses the fraction of faults that become user-visible errors. Our hypothesis is that this increase in AVF is caused by a super-linear increase in “dirty” data residence times in the L2 cache. Using proton beam irradiation, we measured the DUE rates from the write-back cache tags and analyzed the data to show that our hypothesis holds. We utilized a combination of simulation and measurements to help develop and prove this hypothesis. Our investigation reveals two methods by which dirty line residency causes super-linear increases in the L2 cache tags AVF. One is a reduction in the miss rates as we move to the larger cache part, resulting in fewer evictions of data required for architecturally correct execution. The second is the occurrence of strided cache access patterns, which cause a significant increase in the “dirty” residency times of cache lines without increasing the cache miss rate.

NMR spin echo experiments as probes of vortex dynamics in YBa2Cu3O7

Abstract We report 89 Y and 17 O NMR (9 Tesla) spin echo decay (T 2 ) measurements for YBa 2 Cu 3 O 7 . We correct the results to remove effects of 63,65 Cu dipolar coupling in order to isolate effects of vortex dynamics. We confirm vortex localization in the vortex solid state with rms displacements consistent with Langevin dynamical theory, but with motional dynamics at time scales some 10 6 times slower than predicted.