"The 486 topped out at 100MHz (486DX100), but it's performance roughly matched that of the original Pentium running at 60MHz. "
Intel 486 topped out at 100mhz while others went higher than 100mhz. During the time of the 386 and 486 AMD actually had licensed the rights to produce 486 and 386. AMD actually produced chips that were slightly faster than the intel counterparts. I believe AMD maxed out at 120mhz, not sure about cyrix though.