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GROK-LAB: Generating Real On-chip Knowledge for Intra-cluster Delays using Timing Extraction

Benjamin Gojman, Sirisha Nalmela, Nikil Mehta, Nicholas Howarth, and André DeHon
Proceedings of the 21st ACM/SIGDA International Symposium on Field-Programmable Gate Arrays, pp. 81--90, (FPGA, February 11--13, 2013)

Timing Extraction identifies the delay of fine-grained components within an FPGA. From these computed delays, the delay of any path can be calculated. Moreover, a comparison of the fine-grained delays allows a detailed understanding of the amount and type of process variation that exists in the FPGA. To obtain these delays, Timing Extraction measures, using only resources already available in the FPGA, the delay of a small subset of the total paths in the FPGA. We apply Timing Extraction to the Logic Array Block (LAB) on an Altera Cyclone III FPGA to obtain a view of the delay down to near individual LUT granularity, characterizing components with delays on the order of a few hundred picoseconds with a resolution of +/-3.2 ps. This information reveals that the 65nm process used has, on average, random variation of σ/μ=4.0% with components having an average maximum spread of 83ps. Timing Extraction also shows that as VDD decreases from 1.2V to 0.9V in a Cyclone IV 60nm FPGA, paths slow down and variation increases from σ/μ=4.3% to σ/μ=5.8%, a clear indication that lowering VDD magnifies the impact of random variation.

Copyright 2013 ACM, Inc. This is the author's version of the work. It is posted here by permission of ACM for your personal use. Not for redistribution. The definitive version was published in the Proceedings of the International Symposium on Field-Programmable Gate Arrays, (FPGA2013, February 11--13 2013).

N.B. An expanded, journal version appears in TRETs.
A later paper addressesing interconnect appears in FCCM.
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