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Power reduction is nowadays becoming the first consideration in VLSI design. Low power is one of major concerns in deeply scaled CMOS technologies. There have been many methods in very wide rang to achieve this objective. And the Register-Transfer level (RTL) has become the most effective stage in low power VLSI design, according to the significant power optimization impact and accurate power estimation. In this paper, some respective low power design techniques at RTL are re-investigated at tsmc 45 nanometer CMOS technology. Clock gating (CG) is one of the most widely used and effective technique in RTL low power design. Without the enable signal, bus-specific clock gating (BSC) and threshold-based clock gating (TCG) are considered. Also an improved active-driven optimized bus-specific clock gating (OBSC) is proposed in our laboratory. When the enable signal is taken into account, this paper explains local-explicit clock gating (LECG), enhanced clock gating (ECG), waste-toggle-rate-based (WTR) clock gating and the single comparator-based clock gating (SCCG) techniques. Operand isolation is another useful design technique for reducing the power consumption by blocking some redundant operations. Memory splitting is an effective design solution for low power design as well. These techniques have been experimented by using tsmc 45nm technology library and the proposed low-power RTL techniques are evaluated at gate level with logic synthesis results.