M A G M A
2.The 4 and 7 Slot Magma Expansion Systems each add two (2) PCI to PCI Bridges to the PCI Local Bus. The 13 Slot adds three (3) PCI to PCI Bridges to the PCI Local Bus. The 6 Slot adds one (1) bridge. These bridges are the communication paths between the PCI cards and the computer resources. Most computers allow multiple bridges (and thus PCI buses) to be correctly configured. Some computers, unfortunately, place an arbitrary limit on the number of bridge levels that can be traveled during
3.For easier understanding, the PCI Local Bus should be viewed as a “Resource Toll road” that runs from the computer CPU (resource home), through the “Toll Booths” (the PCI bridges), to the “Resource Users” (PCI Cards). As in the case of a real Toll Road, the more Toll Booths you have to slow down a “nanosecond” for, the longer it will take you (your data) to get from the PCI Card to the CPU and back again. Under most circumstances the effect cannot even be detected. However, under other conditions, it can be important to know about.
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 may use either PCIe or PCI host cards in your host computer, depending on available slots and your performance requirements. 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.
36Appendix B Need More Slots?