Software Vault: The Diamond Collection/The Diamond Collection (Software Vault)(Digital Impact).ISO/cdr16/io0395.zip/FTUR01.TXT

Text File | 1995-02-25 | 4KB | 70 lines

THE COPROCESSOR
by Angela Levitt

    The math chip. The floating-point unit. The
coprocessor. Why, darned if those names don't roll so easily
off our tongue that, if the innocent bystander didn't know
better, it might be assumed that we really knew what the
thing does.
    Well, to put it not very briefly, it's like
this: in computers built in days past, there was the central
processing unit, or CPU. Maybe it was an Intel 80286 or 386,
or possibly a Motorola 68020 or 030. In fact, it could have
been any of several processors; my point is that it was
nothing more than an integer CPU (for those who've been out
of school for a while, an integer is a whole number, no
fractions or decimals allowed), actually able to handle only
integer operations, though clever programming could allow it
to also work on the right side of the decimal point.

Isn't that cheating?
    If that sounds contradictory, try this example. Just
imagine an average man who can barely lift his own weight on
a good day after taking his vitamins. Equip him with a
properly-designed pulley system, though, and run a rope over
those pulleys. Presto! He can now lift twice his weight.
Along with all this newfound strength, you'll see another
change: the weight will rise at half the speed our man is
applying to his end of the rope.
    With special programming acting as the pulley system,
the processor did the entire calculating job on your computer
containing an integer CPU, with the result that some
calculations were slow. Other calculations (possibly
equivalent to our guy lifting ten or a hundred times his
weight) were so extremely slow that it was impractical to
use a computer that didn't have a special chip called the
floating point unit, designed to work on the right side of
the decimal point, for those operations. In fact, there are
some software applications that check for floating-point
capability when they're started, and will not run at all if
it isn't there.
    In computers with the CPUs mentioned above, if the
purchaser paid the extra price to get a floating-point unit,
it was in the form of a separate chip. Your current-production
central processing unit, be it an 80486, a 68040, a Pentium,
or a PowerPC, contains both an integer function and a floating
point function, though the two are completely isolated from
each other inside the chip. If your computer doesn't have the
number-crunching capability that you would expect to accompany
that fact, it's because the floating-point function has been
disabled in your chip, not because it isn't there. The
manufacturers tell you this, but they do it in such a sneaky
way that you may not have noticed. If your Intel chip has an
"SX" after the number, or if your Motorola chip contains the
letters "LC," that's your clue. If there's a "DX" or no
letters at all, the FPU still works.
    Why do they put something in the chip, then disable
it? Brace yourself: it's so they can make more money. Nothing
illegal, immoral or fattening here; it's just more efficient
to make lots of one chip than smaller numbers of two chips.

And the payoff?
    Okay, all of that was just so we'd see that there are
two types of operations going on where numbers on both sides
of the decimal are concerned, and two processors to handle
those operations. When numbers must be crunched, the CPU
does the integers (again, whole numbers only) and the FPU
takes the rest. With the two chips working together, the
result is usually a dramatic improvement in computer speed
for complex tasks.
            Copyright 1995 SeeJay Publications