The 6800, 6502, the 6809's clock system differs from other processors of the era. For instance, the Z80 uses a single external clock and the internal steps of the instruction process continue on each transition. This means that the external clock generally runs much faster; 680x designs generally ran at 1 or 2 MHz while the Z80 generally ran at 2 or 4. Internally, the 680x's converted the slower external clock into a higher frequency internal schedule, so on an instruction-for-instruction basis, they ran roughly twice as fast when comparing the external clocks.