The primary factor holding back the 65C816 was the required RAM speed. The 65XX processors required RAM almost twice as fast as the same clocked X86 or 68K. An

The primary factor holding back the 65C816 was the required RAM speed. The 65XX processors required RAM almost twice as fast as the same clocked X86 or 68K. An 8Mhz 65C816 requires 70ns RAM, whereas an 8Mhz 286 or 68K can use 140ns RAM without wait states. 70ns RAM was very expensive until the early 90s, at which point the 65C816 had already missed its window.