INSTALLING A FAST 68881/68882

	The A2620 supports as an option a faster 68881 or 68882 math
chip.  Such a device may greatly speed up math intensive operations over
the standard A2620 math chip.  Motorola supplies both 68881 and 68882
parts in 16MHz, 20MHz, 25MHz, and 33MHz versions.  The A2620 has been
tested with parts running at up to 25MHz.

	For the math chip upgrade, you'll need one of these faster
parts, and a clock module of a lesser or matching frequency rating.  The
clock module is an industry standard 4 pin oscillator can with TTL
compatible output level.  You'll also need a chip puller or flat head
screwdriver, and a soldering iron.  All references to the A2620 board
assume that the Motorola chips are "up" and "left", the memory chips are
"right", and the Coprocessor Slot connector edge is "down" and "left".

	The upgrade is easy to do, but does require the use of a
soldering iron.  Normally the clock module is soldered into the A2620
board as device U204, directly under the math chip socket.  Be sure to
note the orientation of the clock module!  If the module isn't obviously
labelled, it's easy to tell by looking at the pins underneath.  The
shield ground pin will be the one that looks like it's attached directly
to the case of the clock module.  That corresponds with the pin in the
lower right of the U204 position of the A2620.

	Once the clock is in place, the 68881 can be replaced.  If a
chip pulling device isn't available, a flat head screwdriver may be used
to gently loosen the existing 68881.  The faster 68881 or 68882 can be
dropped right into the math ship socket once the standard part is
removed.  Be sure to orient it properly!  Pin 1 of the math chip is
located by a dot in the corner of the device and a gold stem going to
that same corner.  This should be in the lower right corner of the
socket; it says "U201" and "1" just to the right of this corner.

	Once everything's installed, you should switch on the fast
clock.  This is done by moving jumper "J200" to the lower position. 
With that done, replace the A2620 in your Amiga, and power the system
up.  Test the math chip with whatever math-intensive programs you
usually use.  Everything should still work, and it should be faster.

	IF IT DOESN'T FUNCTION, check your work carefully.  You can test
the board with jumper "J200" in the higher position if it's not working
right.  This will run the faster math chip from the 14.3MHz CPU clock
instead of the fast clock, and thus indicate if your fast clock module
is installed incorrectly.  If it continues to fail, this indicates that
your math chip is the incorrect part. 

	IF YOU DON'T SEE ANY SPEEDUP, several things may have happened. 
If "J200" is in the wrong position, you won't run any faster; a faster
math chip needs a faster clock for it to do any good.  If your test
software doesn't use hardware floating point, it'll run faster on the
A2620 than a plain Amiga, just because the 68020 goes faster.  But a
faster math chip won't help.  There are various MandelBrot programs in
the public domain that use hardware floating point when available, and
the Amiga OS V1.3 floating point libraries also access hardware floating
point when it's available.