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Space sensitive cache dumping for post-silicon validation
, S.R. Sarangi, P.R. Panda
Published in Institute of Electrical and Electronics Engineers Inc.
2013
Pages: 497 - 502
Abstract
The internal state of complex modern processors often needs to be dumped out frequently during post-silicon validation. Since the last level cache (considered L2 in this paper) holds most of the state, the volume of data dumped and the transfer time are dominated by the L2 cache. The limited bandwidth to transfer data off-chip coupled with the large size of L2 cache results in stalling the processor for long durations when dumping the cache contents off-chip. To alleviate this, we propose to transfer only those cache lines that were updated since the previous dump. Since maintaining a bit-vector with a separate bit to track the status of individual cache lines is expensive, we propose 2 methods: (i) where a bit tracks multiple cache lines and (ii) an Interval Table which stores only the starting and ending addresses of continuous runs of updated cache lines. Both methods require significantly lesser space compared to a bit-vector, and allow the designer to choose the amount of space to allocate for this design-for-debug (DFD) feature. The impact of reducing storage space is that some non-updated cache lines are dumped too. We attempt to minimize such overheads. Further, the Interval Table is independent of the cache size which makes it ideal for large caches. Through experimentation, we also determine the break-even point below which a t-lines/bit bit-vector is beneficial compared to an Interval Table. © 2013 EDAA.
About the journal
JournalData powered by TypesetProceedings -Design, Automation and Test in Europe, DATE
PublisherData powered by TypesetInstitute of Electrical and Electronics Engineers Inc.
ISSN15301591