and 586 and 686: https://en.wikipedia.org/wiki/Cyrix_6x86 https://en.wikipedia.org/wiki/Cyrix_6x86 They used a Performance Rating, so the "PR166" wasn't actuall

and 586 and 686: https://en.wikipedia.org/wiki/Cyrix_6x86 https://en.wikipedia.org/wiki/Cyrix_6x86 They used a Performance Rating, so the "PR166" wasn't actually running at 166 MHz but 133 MHz. The performance rating was meant to show that it was "equivalent to a 166 MHz Pentium".