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
       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 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 particular, some motherboards do not
       have the interrupt lines from the NPX to the CPU wired properly.

Debian                                           August 28, 1993                                          NPX(4)