PCHB(4)                   OpenBSD Programmer's Manual                  PCHB(4)

NAME
     pchb - PCI-Host Bridge

SYNOPSIS
     pchb* at pci? dev ? function?
     pci* at pchb?

DESCRIPTION
     The pchb driver provides support for PCI-Host adapter-specific functions
     for the following devices:

           i450 PCIset (Orion)
                    Supports additional PCI busses.
           Reliance Computer ROSB4, CNB20HE, CNB20LE
                    Supports additional PCI busses.
           i82424ZX (Saturn)
                    Disables CPU-PCI write posting.
           i82443BX
                    Provides workaround for the following errata: "An incor-
                    rect address may be driven on the DRAM bus, resulting in
                    memory data being fetched from the wrong location."
           i82810/810E, i82815/815E, i82820, i82840
                    Supports the random numbers generator, supplying random
                    bytes from the system's thermal noise.  Driven by periodic
                    checks for available data from the generator, it supplies
                    entropy to the random(4) driver for common usage.

     On i386 systems all other PCI devices of class Bridge and sub-class
     Bridge Host are supported just as PCI attachment point.

     The PowerPC port supports several Apple and Motorola bridges.

SEE ALSO
     intro(4), pci(4), random(4)

HISTORY
     Random number generator support first appeared in OpenBSD 2.7.

AUTHORS
     Support for true RNG present on i82810 chips was added by Michael Shalay-
     eff <mickey@openbsd.org>.

BUGS
     Real RNG probe should fix the PCI scanning loop so it would find the
     Firmware Hub (i82802) which actually contains the RNG device and probe it
     as a real PCI device (i.e., common PCI registers are there).

OpenBSD 3.0                     April 12, 2000                               1
