Q34405: Coprocessor Is Slower in QuickBASIC 4.00b, 4.50 than in 4.00

Article: Q34405
Product(s): See article
Version(s): 3.00 4.00 4.00 4.50
Operating System(s): MS-DOS
Keyword(s): ENDUSER | buglist3.00 buglist4.00 fixlist4.00b SR# S890119-106 | mspl13_basic
Last Modified: 7-FEB-1989

Programs compiled in QuickBASIC Version 4.00 (or the coprocessor
version of QuickBASIC 3.00) generally run faster on a coprocessor than
when compiled in later QuickBASIC Versions (4.00b or 4.50) or in BASIC
Compiler Version 6.00 or 6.00b. There is little speed difference
between versions when run on a computer that has no coprocessor.

This behavior occurs because the coprocessor math routines in Version
4.00 of QuickBASIC are different than the coprocessor math routines
used in later versions of QuickBASIC (4.00b or 4.50) or in the
Microsoft BASIC Compiler 6.00 or 6.00b. The math routines were updated
to correct certain problems in the earlier routines. Additional
coprocessors were required to wait in the new routines, which can
cause slower program-execution time in programs that take advantage of
an installed math coprocessor.

In a benchmark test of floating-point calculations on a computer
equipped with an 80287 coprocessor, QuickBASIC Version 4.00b is
anywhere from 5- to 30-percent slower than QuickBASIC Version 4.00,
depending on the type of coprocessor used. There is no appreciable
speed difference for computers without a coprocessor.

This speed reduction is necessary in Version 4.00b to correct some
erroneous results associated with coprocessor timing-coordination
problems in QuickBASIC Version 4.00 and the coprocessor version
(QB87.EXE) of QuickBASIC Version 3.00.

Microsoft confirmed the timing problems in QuickBASIC Versions 3.00
and 4.00. The problems were corrected in QuickBASIC Version 4.00b (and
later) and in the BASIC Compiler Version 6.00 (and later) and its
copy of QuickBASIC.

A consequence of correcting the timing coordination problems is slower
coprocessor speed in QuickBASIC Version 4.00b or 4.50 than in Version
3.00 or 4.00.

The following benchmark example can be used to compare various
versions of QuickBASIC:

start = TIMER
FOR k% = 1 TO 10000
        u = 1000.45 - 88998.2
        m = 99999! + 23.5
        x = 1.03 * 99.5
        y = 456.3 / 9876.345
        z = 10.3 ^ 2.3
NEXT k%
PRINT "elapsed time="; TIMER - start

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