Towards Scalable Arithmetic Units with Graceful Degradation
Journal article, 2014

This article presents a new family of scalable arithmetic units (ScAUs) targeting resource-constrained, embedded devices. We, first, study the performance, power, area and scalability properties of general adders. Next, suitable error-detection schemes for low-power embedded systems are discussed. As a result, our ScAUs are enhanced with a suitable error-detection scheme, resulting in a Parity-Checked ScAU (PCScAU) design. The PCScAU strikes a flexible trade-off between space and time redundancy, offering dependability similar to high-end techniques for the area and power cost of low-end approaches. An alternative design, the Precision-Scalable Arithmetic Unit (PScAU) maintains throughput with degraded precision in case of hardware failures. The PScAU is targeting dependable applications where latency rather than numerical accuracy is more important. The PScAU's downscaled mode is also interesting for runtime thermal management due to its advantageous power consumption. We implemented and synthesized the PCScAU, PScAU and a few important reference designs (double-, triple- and quadruple-modular-redundancy adders with/without input gating) in 90-nm UMC technology. Overall, the PC-ScAU ranks first in 9 out of 10 power-delay-area (PDA)-product variants. It exhibits 16% area savings and 12% performance speedup for 7% increase in total power consumption, compared to the cheapest form of conventional hardware replication with the same fault coverage. The PDA product of the PCScAU is, thus, reduced by 21%. It is interesting that, while total power slightly increases, the PCScAU static power in fact decreases by 14%. Therefore, for newer technology nodes where the static power component is significant, the PCScAU can also achieve-next to performance and area - significant power improvements.

fault tolerance

error correction


embedded systems

graceful degradation



error detection

low power consumption

scalable design


Computer arithmetic


D. P. Riemens

Netherlands Institute for Neuroscience NIN - KNAW

Georgi Gaydadjiev

Chalmers, Computer Science and Engineering (Chalmers), Computer Engineering (Chalmers)

C. I. de Zeeuw

Erasmus University Rotterdam

C. Strydis

Erasmus University Rotterdam

Transactions on Embedded Computing Systems

1539-9087 (ISSN)

Vol. 13 4

Subject Categories

Computer Engineering



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