Magma
EB7-X8G2 | Appendix A Need More PCIe Slots?
68
The Fan-Out Configuration
The Fan Out addition to the PCI bus hierarchy is at the "peer" level of other existing expansion buses, thus adding
"breadth" to the PCI bus hierarchy, since these buses will be at the same hierarchical level within the system
configuration.
You must ensure that you have the corresponding PCIe to PCIe Expansion System, or chassis to
connect with your host card to support your desired configuration.
In this configuration, you have fewer “Toll Booths” to pass through; therefore the latency is shorter, however you
“sacrifice” a PCIe slot in the host computer for each added chassis.
For clarification, it is necessary to understand that the amount of latency caused by a PCIe
switch (or a PCIe-to-PCI bridge built into some 3
rd
Party PCIe cards) is negligible
(“nanoseconds”) and will not produce any visible effect on most systems. It is only mentioned
here because of certain specialized configurations involving unique PCIe cards with special
software drivers. The total number of logical buses that the data must pass through COULD
make a difference. See
Chapter 5 Troubleshooting
for more information if you suspect this
could be an issue with one of your specialty PCIe cards.
Verify your configuration
Before you start installing your PCIe cards (refer to
Chapter 4 Install PCIe Cards for
more information), you should confirm
that everything is in proper working order. Refer to
Chapter 3 Verify Installation
for guidance in verifying the proper
installation of your Expansion System. For example, the following image shows the division within the Windows Device
Manager display between two Expansion Systems connected in a “Fan-Out” configuration. In this case each expansion
chassis offers only two slots of expansion.