1. Presenter: Hong-Wei Zhuang X-Tracer: A Reconfigurable X- Tolerant Trace Compressor for Silicon Debug Feng Yuan Dept. of Comput. Sci. & Eng., Chinese Univ. of Hong Kong, Hong Kong, China Xiao Liu ; Qiang Xu Design Automation Conference (DAC), 2012 49th ACM/EDAC/IEEE

2. The effectiveness of at-speed silicon debug is constrained by the limited trace buffer size and/or trace port bandwidth, requiring highly efficient trace data compression solutions. As it is usually inevitable to have unknown ‘X’ values during silicon debug, trace compressor should be equipped with X-tolerance feature in order not to significantly degrade error detection capability. 2

3. To tackle this problem, this paper presents a novel reconfigurable X-tolerant trace compressor, namely X-Tracer, which is able to tolerate as many X-bits as possible in the trace streams while guaranteeing high compression ratio, at the cost of little extra design-for-debug hardware. Experimental results on benchmark circuits demonstrate the effectiveness of the proposed technique. 3

4. Silicon debug cannot be an afterthought and has become an essential step in today’s IC design flow. temporal lossy trace compressors  golden vectors  asynchronous clock domains and uninitialized tolerate X-bits in trace-based silicon debug  blocking X-bits  do not know the exact of X-bits  required to obtain as much information 4

5. 5 lossless trace lossless traceCompressors [17] [18] Spatial lossy trace Compressors [19] Temporal lossy trace compressors [20] [21] X-Tracer: A Reconfigurable X-Tolerant Trace Compressorfor Silicon Debug This paper

6. propose a novel reconfigurable MISR-based trace compressor with redundancy that is able to effectively tolerate Xbits develop a trace data extraction algorithm 6

7. cannot be recovered from other MISR outputs Large number of X-bits in trace data will make it fail to find any X- canceling combination 7

8. provide more information redundancy and hence higher possibility to cancel X-bit to tolerate X-bits and reduce the possibility of useful information loss prevent some fixed combination of information bits 8 little area overhead Only half of compression ratio

9. selectively turning on/off the feedback loop from each output the counter value enables us to tradeoff compression ratio and X-tolerant capability our proposed trace compressor can be easily reconfigured 9

10. our objective is to extract as many useful trace bits as possible Since different solutions lead to very different X- canceling combinations, the corresponding extracted trace data may vary significantly. 10

11. three well-defined bit flipping rules  generate a new valid solution  be flipped at the same time  the pivot bits and the last bit in each row cannot be flipped. 11

12. 12

13. X-Tracer vs. Conventional MISR-Based Compressor conducted to evaluate the impact of compression ratio on extracted trace information prove the effectiveness of the reconfigurable trace compressor design 13

14. X-tracer and the proposed trace information extraction algorithm (denoted as “ Xtracer + Extraction”) conventional MISR-based compressor and the proposed extraction algorithm (denoted as “ Conv. +Extraction” 14

15. 15

16. 16

17. proposed X-tracer design, together with the novel algorithms to extract useful trace data out of contaminated trace signatures facilitates to obtain as much trace information as possible while guaranteeing high compression ratio My comment  Novel idea to trace data compressor design for silicon debug 17