Magma PCIe Expansion System EB2 User Manual

 

58            

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 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 

 for more information if you suspect 

this could be an issue with one of your specialty PCIe cards.