A low-energy hybrid radix-4/-8 multiplier for portable multimedia applications

A hybrid radix-4/-8 multiplier is proposed for portable multimedia applications that demand high speed and low energy operation. Depending on the input pattern, the multiplier operates in the radix-8 mode in 56% of the input cases for low power, but reverts to the radix-4 mode in 44% of the slower input cases for high speed. For this, a mode detection circuit determines the mode signal from the input operand in just 2 gate delays. Based on the mode signal, the radix-4/-8 dual Booth encoder generates encoding signals in a hardware efficient way. Moreover, the carry save adder block is selectively activated to reduce power consumption. Compared to a conventional radix-4 multiplier, the proposed hybrid multiplier architecture consumes 33.5% less power at the expense of just 3.3% additional propagation delay, resulting in 31.3% less energy per operation.