A pipelined processor including a combinational logic of several stages, a voltage regulator, a counter, a comparator, and a plurality of stage registers. Each stage register is disposed between two adjacent stages of the combinational logic. The stage register includes a flip-flop, a latch, an XOR gate, and a MUX module. When the high level of a register clock is coming, the flip-flop latches first data at the rising edge, and the latch receives second data during the high level. The data latched by the flip-flop and the latch respectively are compared by the XOR gate. If they are same, the output Error of the XOR gate is low level, and the output of the flip-flop is delivered to the next stage. Otherwise, the output Error of the XOR gate is high level, and the output of the latch is delivered to the next stage.