Wihtout seeing the assembly it is difficult to say but for such a large difference, the culprit often seems to the loop iop cache. If you check the alignment of

Wihtout seeing the assembly it is difficult to say but for such a large difference, the culprit often seems to the loop iop cache. If you check the alignment of the top of the loop instructions (and it inlined away the calls) sometimes you can see an alignment change for some trivial bullshit that has vasat performance impacts because it causes a series of other missed optmizations. That damn loop cache is great for performance when you hit it,but sucks horrible when you don't even think out it and spend days trying to figure out some performance quandry.