MEM(4)               NetBSD/hp700 Kernel Interfaces Manual              MEM(4)

NAME
     mem, kmem -- memory files and memory controller

SYNOPSIS
     mem* at mainbus0

DESCRIPTION
     The mem driver controls and restricts access to the systems memory by the
     hardware buses and the processor.

     It also provides an interface to userland through the special files
     /dev/mem and /dev/kmem.  Physical memory is accessed through /dev/mem,
     while kernel virtual memory is accessed through /dev/kmem.  Access to
     kernel virtual addresses not currently mapped to memory will fail.  On
     hp700, the physical memory range is always contiguous and starts at
     address 0; kernel virtual memory begins at address 0 as well.

     The writeability of the /dev/mem and /dev/kmem special files are con-
     trolled by the system securelevel in addition to the filesystem permis-
     sions.

FILES
     /dev/mem
     /dev/kmem

HISTORY
     The mem driver originates from OpenBSD.  It was ported to NetBSD 1.6 by
     Matthew Fredette.

BUGS
     On some systems featuring a ``Viper'' memory controller, NetBSD may not
     configure bus arbitration correctly, causing the boot process to freeze
     during either mem or cpu(4) device probe.

NetBSD 5.0_STABLE               March 16, 2004               NetBSD 5.0_STABLE
