Epson 486SX - Manual (Page 185)

Math Coprocessor Problems
If the math coprocessor in your system does not seem to be
operating properly, check the following:
1. If you have the 25 MHz model and replaced the 80486SX
microprocessor with an 80487SX chip, make sure you set
jumpers JP1 through JP3 to indicate that you installed a
math coprocessor. See Chapter 6 for instructions.
2. Run the Setup program to make sure the math coprocessor
is listed as installed on the Exit display. If it is listed as not
installed, your dealer may have installed the math
coprocessor incorrectly. See Chapters 2 and 6 for more
information.
Caution
Do not attempt to remove the microprocessor yourself.
Contact your dealer to remove it for you.
3. If your math coprocessor is listed as installed in the Setup
program but still does not seem to be working, test it
by running the System diagnostics program on your
Reference diskette. See Appendix C for instructions.
B-30
Troubleshooting