Lumen Patent Firm
Floating-point multiply-add unit using cascade design
A floating-point fused multiply-add (FMA) unit embodied in an integrated circuit includes a multiplier circuit cascaded with an adder circuit to produce a result A*C+B. To decrease latency, the FMA includes accumulation bypass circuits forwarding an unrounded result of the adder to inputs of the close path and the far path circuits of the adder, and forwarding an exponent result in carry save format to an input of the exponent difference circuit. Also included in the FMA is a multiply-add bypass circuit forwarding the unrounded result to the inputs of the multiplier circuit. The adder circuit includes an exponent difference circuit implemented in parallel with the multiplier circuit; a close path circuit implemented after the exponent difference circuit; and a far path circuit implemented after the exponent difference circuit.
The Board of Trustees of the Leland Stanford Junior University
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additional additional inventional
Sameh Mark
Galal Horowitz