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User:Bjacob/ArithmeticTimingDifferences: Difference between revisions
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User:Bjacob/ArithmeticTimingDifferences (view source)
Revision as of 18:28, 20 June 2013
, 20 June 2013→A significant mass of SSE2-capable CPUs do not have DAZ
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Conventional "wisdom" is that DAZ is available nearly everywhere SSE2 is. | Conventional "wisdom" is that DAZ is available nearly everywhere SSE2 is. | ||
This turns out not to be the case even for Intel CPUs: this [http://people.mozilla.org/~bjacob/ta/results/intel-pentium-m-1.4GHz-family-6-model-9-stepping-5-toshiba-tecra/ Pentium M] supports SSE2 but evidently [http://people.mozilla.org/~bjacob/ta/results/intel-pentium-m-1.4GHz-family-6-model-9-stepping-5-toshiba-tecra/time-math-x86-32-sse2-DAZ-FTZ.txt doesn't support DAZ]. | This turns out not to be the case even for Intel CPUs: this [http://people.mozilla.org/~bjacob/ta/results/intel-pentium-m-1.4GHz-family-6-model-9-stepping-5-toshiba-tecra/ Pentium M] supports SSE2 but evidently [http://people.mozilla.org/~bjacob/ta/results/intel-pentium-m-1.4GHz-family-6-model-9-stepping-5-toshiba-tecra/time-math-x86-32-sse2-DAZ-FTZ.txt doesn't support DAZ]. As a result, timings are all over the place, even on just additions, as soon as denormals are involved. | ||
It is also reported that some early Pentium 4 CPUs were in the same case. Conversely, not ''all'' Pentium M's are affected (here is an [http://people.mozilla.org/~bjacob/ta/results/intel-pentium-m-1.6GHz-family-6-model-13-stepping-6-dell-inspiron600m-gavin/ unaffected one]). | It is also reported that some early Pentium 4 CPUs were in the same case. Conversely, not ''all'' Pentium M's are affected (here is an [http://people.mozilla.org/~bjacob/ta/results/intel-pentium-m-1.6GHz-family-6-model-13-stepping-6-dell-inspiron600m-gavin/ unaffected one]). | ||