Product specifications

the "downstream" or higher numbered PCI bus). In the case of the
MAGMA PCI Expansion System, the PCI host interface card, which is
plugged into an available slot on your host computer, has at its
"upstream" side (Bus 0) and at its "downstream" side the cable (Bus 1).
The PCI expansion interface also has a PPB on board and its
"upstream" side is attached to the cable bus (Bus 1) and its
"downstream" side is attached to the expansion motherboard (Bus 2).
Inserting a host interface into an available slot in the motherboard
results in its primary bus being at (Bus 2), its secondary bus (the cable
bus) being at (Bus 3) and the PCI expansion interface in the second
motherboard is (Bus 4).
PCI Card Conflicts
If you determine that one PCI card is interfering with the operation of
another card, first try reorganizing the cards on the motherboard.
Moving the cards around can change the order in which the cards are
configured by the system firmware (whether console code or BIOS
code) and will go a long way toward resolving module conflicts.
Console Firmware Issues
Different systems have different names for their console firmware. On
an IBM-PC compatible the firmware is referred to as the system's
"BIOS" code. For a SUN workstation the computer console code is
called OBP (OpenBootProm). For a Macintosh computer the console
code is called "OpenFirmware" code. Regardless of what it's called, the
console firmware will perform the same basic set of functions. In a
nutshell, the console firmware must provide a set of hardware or
architecture-specific functions and routines that are called during the
early phases of system startup. Specifically, these functions and
callable routines allow the PCI devices in a host computer to be
recognized and configured for use by the soon-to-be-running system.
The portion of the PCI Local Bus Specification that directly addresses
this class of code is the PCI BIOS Specification. A similar specification
for use by systems that are not IBM-PC compatible is the IEEE 1275-
1994 OpenFirmware Bus Binding Specification. These two different
specifications are complimentary and form a consistent methodology
that allows for PCI option identification and configuration during the
initial phases of booting the target operating system.
During configuration of your system's PCI cards, the PCI bus must be
probed in order to determine which, if any, PCI cards are present in your
system. The probe instructions used ensure that PCI slots that contain
valid cards are configured into your system in a consistent and reliable
manner and that any invalid option card, or empty option slot, is ignored.
In theory, the console configuration code should be able to traverse up
to 255 PCI buses in your system detecting all installed cards and