The Original IBM AT used a 6Mhz 286, and then an 8Mhz 286, and then modified the ROMSs so you could not make a 6Mhz into an 8Mhz by swapping the crystal. Other vendors cranked up the speed to 10, 12, 16, 20 and finally 25Mhz.

IBM PS2s went for 10Mhz 1 Wait state, and 10Mhz zero wait states.

A 25Mhz 286 rivaled a 386 DX in speed in benchmarks, but was left in the just for any 32-bit apps. I had a 20Mhz 286 with 4mb of ram, but only for DOS programs such as CA-General Ledger.

The AT was still the model for clones until the PCI bus came out. It's even in the names of devices and peripherals: ATX motherboard form factor, ATA (IDE) drive interface, etc.