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M A G M A

Multiple PCI Expansion System Configurations

The PCI Local Bus Specification defines the PCI bus as a hierarchical bus, where PCI to PCI Bridges (PPBs) may be used to add "levels" to the PCI bus hierarchy. Because hierarchies are organized systems arranged into different levels, you can take advantage of this automatic organizing and layering to expand the number of available PCI slots beyond the number available in your computer’s motherboard.

You can easily add two or more Magma expansion systems to your current system in either a "fan-out" or "daisy-chain" configuration. Each of these configurations has advantages and uses. To determine which type of configuration you wish to use, you should first understand a few basic facts:

1.In a desktop computer, the bios enumerates automatically behind PCI bridges. In the Magma configuration, the bios finds the Magma host card in a PCI Express slot. The bios configures it, and then looks beyond it to find any PCI cards installed in the expansion chassis. The bios then configures the cards and allocates resources. Empty PCI slots are ignored during configuration.

In theory, your computer “should” be able to travel across up to 255 PCI buses to identify and configure all installed PCI cards. Unfortunately, not all computers are created equal. The 255 PCI bus limit is actually a theoretical maximum. The practical limit is somewhat lower, but should still be a fairly large number.

In a desktop computer the bus numbers tend to be lower (0, 1, 2, etc.). Once the bios is finished configuring everything and assigning resources, the Operating System starts loading and activates the PCI cards found.

When adding more Expansion Systems to an existing system, be sure to connect and test them “one-at-a-time.” This will allow you to quickly resolve any connectivity, or other, issues right at the start. DO NOT INSTALL any 3rd Party PCI cards into any system until ALL attached systems are working correctly.

36Appendix B Need More Slots?