PII-266 (spec SL2W7), PII (spec SL2W8) -> 333 (ok, due to down-binning by intel)
PIII-450 (spec SL35D) are actually PIII-600MHz (ok, due to down-binning by intel)
Am486DX2 (66/80MHz) down binned 100MHz parts (QC failed, Malaysia, fab25253)
AMD K7 500/550MHz are mostly down binned 600MHz parts (open cartridge and look an CPU print)
AMD K7 1.0-1.33GHz (serial AXIA / AZIA [second line], Y [third line]) are actually 1.5GHz+ parts
Dixon/Mobile Celeron is a Mobile PII with only 128KB L2 activated
FC-Celeron is a FC-Pentium II (Coppermine) with only 128KB L2 activated
Celeron 900MHz (Tualatin 256) with S-spec SL68V is taken from the 1.2+GHz production line.
It's because intel closes it's PIII based production lines soon (date of writing Aug 02, 2002).