Epson Apex 20020 - Manual (Page 127)

Math coprocessor clock speed. If you install an 80287 math
coprocessor, you may need to set the jumpers for a different
clock speed. The jumpers determine the speed of the
coprocessor.
Since it is easy to damage a math coprocessor, you should
have your Epson Customer Care Center install it for you.
In addition to checking the jumper settings, you also need
to run the Setup program to change the settings in the
CMOS RAM, and you may want to test the coprocessor
with the System Diagnostics program. See Chapter 2 for
instructions on running Setup. See Appendix C for
instructions on testing the math coprocessor.
The table below shows the functions for the jumpers on the
main circuit board.
Main circuit board jumper settings
Jumper number Function
1 2 3 4 5
A
B
A A
B A
A B
B B
A
B
* Default setting
1 wait state for EPROM access *
2 wait states for EPROM access
1 wait state for 16-bit option card *
2 wait states for 16-bit option card
3 wait states for 16-bit option card
4 wait states for 16-bit option card *
A Set coprocessor clock at 8 MHz *
B Set coprocessor at 1/3 of CPU speed
To access the main circuit board jumpers, you must remove the
memory card from the computer, as described above. Do not try
to access the jumpers while this card is still in the computer.
The locations of jumpers J1-J5 on the main circuit board are
shown in the following illustration. Refer to the table above to
set them as needed.
Installing Option Cards 5-11