Sklansky adder array vs PROM

Discussion in 'General Electronics Chat' started by hp1729, Dec 13, 2015.

  1. hp1729

    Thread Starter Well-Known Member

    Nov 23, 2015
    Have PROMs gotten fast enough to replace the Sklansky / Tree array of adders? A 4 by 4 adder or multiplier could be implemented with a 256 x 8 PROM. An 8 by 8 with a 1 MB PROM.
  2. sailorjoe


    Jun 4, 2013
    The only way to answer your question is to look at the specs for specific chips and do a comparison of access times. In the absence of a physical technology it's logical to assume that a circuit topology that doesn't have to wait for carry bit propagation is the faster circuit. That would be the advantage of the PROM based circuit, but only IF the propagation time of the PROM is better than the two or more propagation times of cascaded adder circuits.