As an alternative to floating-point, several workers have proposed the use
of a logarithmic number system, in which a real number is represented as a
fixed-point logarithm. Multiplication and division therefore proceed in
minimal time with no rounding error. However, the system can only offer an
overall advantage if addition and subtraction can be performed with speed
and accuracy at least equal to that of floating-point, but this has
hitherto been difficult to achieve. We will present a number of original
techniques by which this has now been accomplished. We will then
demonstrate by means of simulations that the logarithmic system offers
around twofold improvements in speed and accuracy, and finally will
describe a new European collaborative project which aims to develop a
logarithmic microprocessor during the next three years.