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PCHB(4)                  BSD Kernel Interfaces Manual                  PCHB(4)

NAME
     pchb -- PCI-Host Bridge

SYNOPSIS
     pchb* at pci?
     pci* at pchb?

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

           i450 PCIset (Orion)
                   Supports additional PCI buses.

           Reliance Computer ROSB4, CNB20HE, CNB20LE
                   Supports additional PCI buses.

           i82424ZX (Saturn)
                   Disables CPU-PCI write posting.

           i82443BX
                   Provides workaround for the following errata: "An incorrect
                   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 amd64 and i386 systems, most PCI devices of class Bridge and sub-class
     Bridge Host are supported just as PCI attachment points.  A few other
     system control devices not listed here are supported by pchb.

     The macppc 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
     Shalayeff <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).

BSD                             April 29, 2017                             BSD