Using this tool: http://www.cacheprof.org/ I got this output: http://www.enme.ucalgary.ca/~nascheme/python/cache.out http://www.enme.ucalgary.ca/~nascheme/python/cache-152.out The cache miss rate for eval_code2 is about two times larger in 1.6. The overall miss rate is about the same. Is this significant? I suspect that the instruction cache is more important for eval_code2. Unfortunately cacheprof can only profile the L1 data cache. Perhaps someone will find this data useful or interesting. Neil