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

NAME
       npx -- Numeric Processing Extension coprocessor

SYNOPSIS
       device npx
       hint.npx.0.at="nexus"
       hint.npx.0.port="0x0F0"
       hint.npx.0.flags="0x0"
       hint.npx.0.irq="13"

DESCRIPTION
       The  npx	 driver	enables	the use	of the system's	Numeric	Processing Ex-
       tension coprocessor.  Numeric processing	extensions are present in sys-
       tems with 486DX CPUs and	in systems with	 387  or  487SX	 coprocessors.
       The  npx	driver is required for proper system functioning.  If there is
       no NPX in the system, the system	will not boot.

       The flags for npx0 are:

       0x01    do not use the NPX registers to optimize	bcopy.
       0x02    do not use the NPX registers to optimize	bzero.
       0x04    do not use the NPX registers to optimize	copyin or copyout.

       The NPX registers are normally used to  optimize	 copying  and  zeroing
       when all	of the following conditions are	satisfied:

       1.   cpu	I586_CPU is an option
       2.   the	CPU is an i586 (perhaps	not a Pentium)
       3.   the	probe for npx0 succeeds
       4.   INT	16 exception handling works.

       Then  copying  and  zeroing using the NPX registers is normally 30-100%
       faster.

       The flags can be	used to	control	cases where it does  not  work	or  is
       slower.	Setting	them at	boot time using	hints works correctly (the op-
       timizations  are	not used until later in	the bootstrap when npx0	is at-
       tached).

BUGS
       There are lots of them, especially on old cheap motherboards.  In  par-
       ticular,	some motherboards do not have the interrupt lines from the NPX
       to the CPU wired	properly.

FreeBSD	14.3			August 28, 1993				NPX(4)

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<https://man.freebsd.org/cgi/man.cgi?query=npx&sektion=4&manpath=FreeBSD+14.3-RELEASE+and+Ports>

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