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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 Extension
     coprocessor.   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.  If there is no NPX in the sys-
     tem, 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  optimizations
     are not used until later in the bootstrap when npx0 is attached).

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

FreeBSD ports 15.quarterly	 August 28, 1993			  NPX(4)

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