18
CMX32M cpuModule
BDM-610000075
Rev B
Selecting the Stack Order for the CMX32M
There are several things to consider when selecting the order of boards in the stack. Before selecting the order,
be sure to determine which bus connector on each board is the “Active” bus. Typically, if a peripheral module has
both PCIe and PCI bus connectors, only the PCIe is active and the PCI is pass-through. The following is a list of
rules to use to determine the stack order:
1.
Any board that uses a PCIe x16, x8, or x4 link must be stacked below the CPU. It is recommended that
these boards be directly below the CPU. See
on page 49 for details.
2.
Any boards that a SATA link must be stacked above the CPU. An example of this is hard drive carrier
boards.
3.
Any board that uses a PCIe or SATA link must be within six boards of the CPU.
4.
The PCIe connectors above and below the CPU have completely separate signals. Therefore it is
possible to attach boards to the PCIe connector above and below the CPU.
5.
To preserve power integrity, it is recommended that there be no more than six boards between the CPU
and the power supply.
6.
In order to maintain maximum performance over the full temperature range, it is recommended that
a PCIe spacer be used between the CPU and any board immediately above it.
7.
A maximum of four PCI boards may be attached to any PCI bus.
8.
The PCIe to PCI bridge must be at one end of the PCI bus segment, and all of the peripheral cards at
the other end. There may be up to eight PCI pass-through connectors between the PCIe to PCI bridge
and the peripheral cards.
9.
There must be no more than two boards between the first PCI peripheral and the last PCI peripheral.
If there are four PCI peripheral cards in a PCI bus segment, there may not be any PCI pass-through
connections between them.
Summary of Contents for BDM-610000075
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