Message-ID: <2809@ncsu.UUCP>
Date: Wed, 6-Mar-85 10:02:36 EST
Article-I.D.: ncsu.2809
Posted: Wed Mar 6 10:02:36 1985
Date-Received: Sat, 9-Mar-85 10:43:55 EST
Organization: N.C. State University, Raleigh
Lines: 41
I am trying to find out execution times for floating-point instructions
for a DEC PRO-350. This is needed for analysis of some experiments
we conducted to compared predicted and actual execution times of some
signal-processing type algorithms on microprocessors. So far, DEC has
been unhelpful. It appears that the PRO-350 has a KEF11-CA microcode
option that adds some 46 f.p. instructions to the integer instruction
set, rather than the FPF-11 f.p. co-processor. I found some times
listed for KEF11A microcode option in the 1979-80 DEC Microcomputer
Processor Handbook, but am suspicious of these old figures:
ADDD add double 42.45 microsec
SUBD subtract double 43.35 microsec
MULD multiply double 193.05 microsec
DIVD divide double 239.25 microsec.
There appears to be no logarithm instruction (would like times if there is
one).
I would appreciate any data or pointers on this (like: who knows at DEC,
what manual contains this info, etc.).
Related to this, we ran the same set of programs on the DEC PRO-350 and
on an IBM PC/XT, and have total times for both: for both, the programs
were written in C, and were identical. The PRO was running Venix, the
PC/XT (with 8087) was running PC-DOS 2.02 and we used the DeSmet C compiler.
We were surprised that the PC/XT times were 20-50% FASTER than the PRO!
This seemed particularly odd, as the DeSmet compiler generates rather
inefficient 8087 code (subroutine calls for each operation). Any comments
on this?
Thanks for any help anyone can give.
Phil Shaffer
P.S. I just talked with a "hardware support specialist" from DEC, and
he said (1) the PRO-350 has a FP-11 coprocessor (KEF-11-CA is the
configuration number); (2) "the execution time is in the range of
1.11 MHz to 5 MHz depending on the function of the CPU." He said
he couldn't be more specific; he obviously didn't know what he was
talking about.
Is anybody knowledgeable from DEC out there?