npx(4) - NetBSD Manual Pages

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NPX(4)               NetBSD/i386 Kernel Interfaces Manual               NPX(4)


NAME

     npx -- Numeric Processing Extension coprocessor and emulator


SYNOPSIS

     options MATH_EMULATE
     npx0 at isa? port "IO_NPX0" irq 13
     npx* at acpi?
     npx* at pnpbios? index ?


DESCRIPTION

     The npx driver enables the use of the system's Numeric Processing Exten-
     sion coprocessor, if one is present.  Numeric processing extensions are
     present in systems with 486DX CPUs and in systems with 387 or 487SX
     coprocessors.  The npx driver is required for proper system functioning
     regardless of whether or not an NPX is present.

     If there is no NPX present in the system, the "MATH_EMULATE" option must
     be defined in the kernel configuration file.  It will provide support for
     the instructions normally executed by the NPX.  If there is no NPX in the
     system and the kernel is not built with math emulation, the system will
     not boot.


SEE ALSO

     acpi(4), isa(4), pnpbios(4)


BUGS

     The emulator is much slower than the NPX coprocessor.  This will result
     in poor floating-point math performance if the emulator must be used.

     There are lots of them, especially on cheap motherboards.  In particular,
     some motherboards do not have the interrupt lines from the NPX to the CPU
     wired properly.  If this is the case, the emulator must be used if con-
     sistent system operation is desired.

     Emulation of the transcendental functions instructions is incorrect.
     Emulation of other instructions is suspect.

NetBSD 3.1                      August 6, 1993                      NetBSD 3.1