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PCHB(4) Device Drivers Manual PCHB(4)

pchbPCI-Host Bridge

pchb* at pci?
pci* at pchb?

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.
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.

intro(4), pci(4), random(4)

Random number generator support first appeared in OpenBSD 2.7.

Support for true RNG present on i82810 chips was added by Michael Shalayeff <>.

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).

July 16, 2013 OpenBSD-6.7