National Instruments PCI-8331 - Manual (Page 11)

Chapter 1 Introduction
© National Instruments Corporation 1-3 MXI-4 Series User Manual
Larger MXI-4 Systems
Using multiple MXI-4 dyads, large PCI/PXI/CompactPCI systems can be
created. The PCI specification makes provisions for up to 255 bus segments
to simultaneously exist in a PCI hierarchy and MXI-4 hardware provides
everything needed to support those provisions.
Notes Keep in mind that some chassis and PCs have more than one PCI bus segment.
The host configuration software (BIOS and OS) and device drivers must support the
number of bus segments and PCI devices that you intend to use.
Figure 1-2 shows how MXI-4 cards can be used to connect multiple
expansion chassis to a PC in both a star and daisy chain topology. The
PC that is shown at the root of the PCI hierarchy in this example could
instead be a PXI/CompactPCI chassis with an embedded controller in its
controller slot. The star topology will give higher performance than the
daisy chain because it minimizes the number of MXI-4 dyads between the
expansion cards and the PC.