The worst part of the P4 was when it went off into la-la land for 4000 cycles of replay. Did you issue a locked instruction? 4000 cycle penalty. Use rep ; movs? 4000 cycle penalty. Some weird internal condition with a misaligned store? 4000 cycle penalty. One could optimize to improve performance in those cases, but the performance glass jaws on the P4 were all consuming.
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The worst part of the P4 was when it went off into la-la land for 4000 cycles of replay. Did you issue a locked instruction? 4000 cycle penalty. Use rep ; movs? 4000 cycle penalty. Some weird internal condition with a misaligned store? 4000 cycle penalty. One could optimize to improve performance in those cases, but the performance glass jaws on the P4 were all consuming.