Keywords—Addition, mathematic, non-speculative adder, speculative adder, delay, power consumption. 1. INTRODUCTION
Adders …show more content…
5. 16-bit Non-Speculative Han-Carlson Adder
This adder has five stages in which the middle three stages are resembles with the Kogge-Stone structure. The advantage of this adder is that it uses much less cells and its shorter span wires than the Kogge-Stone adder and thus there is reduction in complexity at the cost of an additional stage for carry-merge path. The main drawback of this adder is that increased power consumption.
4. PROPOSED WORK
This work 16-bit speculative Han-Carlson adder (HCA) is proposed. Speculative prefix adders can be subdivided in five stages: pre-processing, speculative prefix-processing, post-processing, error detection and error correction. The error correction stage is off the critical path, as it has two clock cycles to obtain the exact sum when speculation fails.
4.1 Pre-processing stage The propagate and generate signals are computed as in equations (1) & (2).
4.2 Speculative Prefix-processing stage
The last Kogge-Stone row of the n = 16 bit graph is shortened, resulting in a speculative prefix-processing stage with K = 8 is shown in Fig. 6. The length of the propagate chains is K = 8 only for i = 9,11,13,15, while for i = 10,12,14 the propagate chain length is K+1 = 9. The computed propagate and generate signals for the speculative Han-Carlson architecture