INT 75 - IRQ13 - MATH COPROCESSOR EXCEPTION (AT and up)
   redirected to INT 02 by the BIOS, for compatibility with the PC
Notes:  may be masked by setting bit 5 on I/O port A1h
        not all clones wire the coprocessor to generate this IRQ; some systems
          generate an NMI (see INT 02) or assert the -ERROR pin on the CPU
          (see INT 10"COPROCESSOR")
        under DESQview, only the INT 15h vector and BASIC segment address (the
          word at 0000h:0510h) may be assumed to be valid for the handler's
          process
SeeAlso: INT 5D