Area Efficient and Fast Combined Binary/Decimal Floating Point Fused Multiply Add Unit

Abstract

In this work we present a new 64-bit floating point Fused Multiply Add (FMA) unit that can perform both binary and decimal addition, multiplication, and fused-multiply-add operations. The presented FMA has 6 percent less delay than the fastest stand-alone decimal unit and 23 percent less area than both binary and decimal units together. These results were achieved by the use of: 1) column by column reduction to reduce the partial products in the multiplier tree, 2) a new leading zeros detector that produces its output in base-3 to simplify the normalization shifting in the binary datapath, 3) the use of a redundant adder to perform the final addition, 4) using a new rounding-while-redundant technique to hide the rounding delay and remove it from the critical path, and 5) using a new simple conversion technique from redundant to binary/decimal.