Computation of √x/d in a very high radix combined division/square-root unit with scaling and selection by rounding

作     者：Antelo, E Lang, T Bruguera, JD 

作者机构：Univ Santiago de Compostela Dept Electron & Comp Santiago De Compostela Spain Univ Calif Irvine Dept Elect & Comp Engn Irvine CA 92697 USA 

出 版 物：《IEEE TRANSACTIONS ON COMPUTERS》 (IEEE Trans Comput)

年 卷 期：1998年第47卷第2期

页      面：152-161页

核心收录：

学科分类：0808[工学-电气工程] 08[工学] 0812[工学-计算机科学与技术（可授工学、理学学位）] 

基　　金：Ministry of Education and Science, MES Comisión Interministerial de Ciencia y Tecnología, CICYT, (TIC96-1125) Comisión Interministerial de Ciencia y Tecnología, CICYT Xunta de Galicia, (XUGA-20605B95) Xunta de Galicia 

主　　题：digit-recurrence algorithm division high-radix methods inverse square-root square-root 

摘      要：A very-high radix digit-recurrence algorithm for the operation root s/d is developed, with residual scaling and digit selection by rounding. This is an extension of the division and square-root algorithms presented previously, and for which a combined unit was shown to provide a fast execution of these operations. The architecture of a combined unit to execute division, square-root, and root x/d is described, with inverse square-root as a special case. A comparison with the corresponding combined division and square-root unit shows a similar cycle time and an increase of one cycle for the extended operation with respect to square-root. To obtain an exactly rounded result for the extended operation a datapath of about 2n bits is needed. An alternative is proposed which requires approximately the same width as for square-root, but produces a result with an error of less than one ulp. The area increase with respect to the division and square root unit should be no greater than 15 percent. Consequently, whenever a Very high radix unit for division and square-root seems suitable, it might be profitable to implement the extended unit instead.