Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site ucbvax.ARPA Path: utzoo!watmath!clyde!burl!ulysses!ucbvax!info-vax From: info-vax@ucbvax.ARPA Newsgroups: fa.info-vax Subject: speed of single/double precision calculations Message-ID: <3468@ucbvax.ARPA> Date: Mon, 26-Nov-84 02:40:40 EST Article-I.D.: ucbvax.3468 Posted: Mon Nov 26 02:40:40 1984 Date-Received: Tue, 27-Nov-84 03:40:58 EST Sender: daemon@ucbvax.ARPA Organization: University of California at Berkeley Lines: 46 From: Tony Li From: Bill Mitchell Does anyone have approximate instruction timings for single and double precision floating point operations on a 780? I don't need anything extremely accurate; the question I'm trying to answer is how much speedup might result from doing all C floating point calculations in single precision rather than double precision. These are some instruction timings that I have. If you disregard the time that C takes to do CVTFD and CVTDF, I'd say that you'd gain roughly a factor of 4 or better. These timings were done by Oregon Software on a 780. All times are in microseconds. I don't know if they had an FPA, but from the figures, I'd guess that they did. Cheers, Tony ;-) ADD 40 ADDF2 Add F_floating 2 operand [1.60] 41 ADDF3 Add F_floating 3 operand [2.00] 60 ADDD2 Add D_floating 2 operand [7.80] 61 ADDD3 Add D_floating 3 operand [8.00] SUB 42 SUBF2 Subtract F_floating 2 operand [1.40] 43 SUBF3 Subtract F_floating 3 operand [1.80] 62 SUBD2 Subtract D_floating 2 operand [7.20] 63 SUBD3 Subtract D_floating 3 operand [7.40] MUL 44 MULF2 Multiply F_floating 2 operand [5.20] 45 MULF3 Multiply F_floating 3 operand [5.80] 64 MULD2 Multiply D_floating 2 operand [17.60] 65 MULD3 Multiply D_floating 3 operand [18.00] DIV 46 DIVF2 Divide F_floating 2 operand [7.60] 47 DIVF3 Divide F_floating 3 operand [8.20] 66 DIVD2 Divide D_floating 2 operand [42.80] 67 DIVD3 Divide D_floating 3 operand [43.00]