Leading Zero Anticipator Research Articles

선행 제로 예측기를 이용한 고속 연산 십진 부동소수점 가산기 설계

선행 제로 예측기를 이용한 고속 연산 십진 부동소수점 가산기 설계

A 6.2-GFlops Floating-Point Multiply-Accumulator With Conditional Normalization

A pipelined single-precision floating-point multiply-accumulator (FPMAC) featuring a single-cycle accumulate loop using base 32 and internal carry-save arithmetic with delayed addition is described. A combination of algorithmic, logic, and circuit techniques enables multiply-accumulate operations at speeds exceeding 3 GHz with single-cycle throughput. The optimizations allow removal of the costly normalization step from the critical accumulate loop. This logic is conditionally powered down using dynamic sleep transistors on long accumulate operations, saving active and leakage power. In addition, an improved leading-zero anticipator (LZA) and overflow prediction logic applicable to carry-save format is presented. In a 90-nm seven-metal dual-V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> CMOS process, the 2 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> custom design contains 230K transistors. The fully functional first silicon achieves 6.2 GFlops of performance while dissipating 1.2 W at 3.1 GHz, 1.3-V supply

Comments on "Leading-zero anticipatory logic for high-speed floating point addition" [with reply

For original article see H. Suzuki, H. Morinaka, H. Makino, Y. Nakase, K. Mashiko and T. Sumi, ibid., vol.31, pp.1157-69 (Aug. 1996). I have read with a great interest the article by H. Suzuki et al. I am familiar with their work, and I found their approach interesting. The idea used to simplify the leading zero anticipator (LZA) I found innovative and an improvement over the one used in the IBM RS/6000. However, I found the LZ counter circuit shown in the paper similar to the LZ counter circuit that I have published previously in the period from 1992-94.

Leading-zero anticipator (LZA) in the IBM RISC System/6000 floating-point execution unit

This paper presents a novel technique used in the multiply-add-fused (MAF) unit of the IBM RISC System/6000* (RS/6000) processor for normalizing the floating-point results. Unlike the conventional procedures applied thus far, the so-called leading-zero anticipator (LZA) of the RS/6000 carries out processing of the leading zeros and ones in parallel with floating-point addition. Therefore, the new circuitry reduces the total latency of the MAF unit by enabling the normalization and addition to take place in a single cycle.