Abstract for:    EE385B
                 Wed 7/26/95 at 12:15 in ERL 401


          An Analysis of Division Algorithms and Implementations

                            Stuart Oberman



  Floating-point  division is generally  regarded as a  low frequency,  high
latency operation  in typical  floating-point applications.    However,  the
increasing emphasis on high performance graphics and the industry-wide usage
of performance benchmarks forces processor designers to pay close  attention
to all aspects of floating-point computation.

  In  this talk,  the  four major  classes of  division algorithms  will  be
presented, namely digit recurrence,  functional iteration, very-high  radix,
and variable  latency.    Digit  recurrence  algorithms, such  as  SRT,  use
subtraction as the  fundamental operator,  and they converge  to a  quotient
linearly.    Division  by  functional  iteration  converges  to  a  quotient
quadratically using multiplication.  Very high radix division algorithms are
similar to digit recurrence algorithms, but they incorporate  multiplication
to reduce the  latency.   Variable  latency division  algorithms reduce  the
average latency to form  the quotient.   These algorithms are explained  and
compared throughout the talk.  It is found that for low-cost implementations
where chip area must be minimized, digit recurrence algorithms are suitable.
An implementation of division by functional iteration can provide the lowest
latency for typical multiplier latencies.  Variable latency algorithms  show
promise for simultaneously minimizing average latency while also  minimizing
area.  Topics of continuing research will also be presented.