Fan-Out - Magma PE6R4-I User Manual

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 PCI 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 PCI
Expansion System, or PCI Expansion System, chassis to
connect with your host card and support your desired
configuration.
In this configuration, you have fewer "Toll Booths" to pass through;
therefore the latency is shorter, however you "sacrifice" more PCIe slots
on the host computer, which may not always be an option.
For clarification, it is necessary to understand that the amount
of latency caused by any PCI Bridge (even those built into a 3
Party PCI card or the computer motherboard itself) is negligible
("nanoseconds") and will not produce any visible effect on most
systems. It is only mentioned here because on a few rare
configurations which use some unique PCI cards with special
software drivers, the total number of PCI buses that the data
must pass through COULD make a difference. See
Troubleshooting
be an issue with one of your specialty PCI cards.
38 Appendix B Need More Slots?
for more information if you suspect this could
rd
Chapter 6