michael@nvuxd.UUCP (M.CAIN) (03/12/85)
The exact nature of the benchmark can, of course, influence the results. We've tried some floating point signal processing routines, and the Pro350 and PC/XT (both running VENIX) were pretty close (on the order of 5-10%). I suspect that this was so because the routines were manipulating large arrays of floating point numbers, and the PC was slowed substantially by its 8-bit bus. I seem to recall seeing at least one "benchmark" that showed the PC with 8087 was about 0.60 VAX, but used so few floating point values that they could all be kept in the 8087 registers. Michael Cain Bell Communications Research ..!bellcore!nvuxd!michael
wjafyfe@watmath.UUCP (Andy Fyfe) (03/15/85)
There are a number of DEC PRO 350s around the campus here. A number of
them are used by the applied math department for various numerical things
(with many of the programs written in basic). We found out that the
basic square root function is hopelessly inaccurate -- no more than
about 3 significant digits. Raising to the power .5 is much better.
Is this the fault of basic, or the floating point hardware?
--Andy Fyfe ...!{decvax, allegra, ihnp4, et. al}!watmath!wjafyfe
wjafyfe@waterloo.csnetdan@rna.UUCP (03/15/85)
x You are basically right. The Pro 350 uses the F-11 chip set. The KEF-11 chip is a floating point microcode extension. The time you quote for floating point performance are for the 11/23 with the KEF-11 but should be close to correct. DEC also makes a bit-slice FPF-11 which is plug compatible with the KEF-11 chip and is said to be 5X faster than the KEF-11 chip. You should be able to use that board if you provide it with power (it normally obtains power from either the Qbus or Unibus slot). There is no logarithm instruction (or any transcendentals) on any PDP-11 machine. My benchmarks on an 11/23 and a PC/XT (amongst other machines) were posted a while ago. For floating point performance, the 11/23 rated at .034 of an 11/780 (w/ FPA) while the PC/XT rated at .13, i.e. the PC/XT should be as much as 3-4X faster than 11/23 (or the PRO350) in floating point. Overall, however, the 11/23 rated at .16 of the 11/780 while the PC/XT rated at .12 . The tested 11/23 had a fast disk. I further understand that the PRO350 disk is abysmally slow, so it would not rate so high. Incidentally, the 11/73 floating point rates at .16, overall .35, so the PRO380 should be more reasonable since it also uses the J-11 chip.