Magma EBU, EB7R-x8, EB7-x8 user manual Fan-Out

M A G M A

Fan-Out

For reasons described in bullet #3 above, we recommend using a fan- out configuration when you need to add successive PCIe expansion systems to the host computer. This 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’ve “sacrificed” another PCIe slot from the host computer, which may not always be an option.

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 3rd 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 6 Troubleshooting for more information if you suspect this could be an issue with one of your specialty PCIe cards.

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