Allied Telesis AT-2931SX - Manual (Page 114)

Troubleshooting
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Solution: When the system is booted up without an adapter, the bus
operates at the lowest mode which is PCI. This problem can be corrected
by rebooting the system.
Problem: The adapter may not perform at optimal level when it is added
by the Hot Plug application on some systems.
Solution: The system BIOS, in some systems, does not set the cache line
size and the latency timer, after the adapter is added by the Hot Plug
application. This problem can be corrected by rebooting the system.
Problem: The adapter cannot be seen on the PCI BUS.
Solution: This is because some of the older servers are advertising
themselves as PCI-X capable systems. This causes the adapter to
operate in PCI-X mode; therefore; it is not seen by the PCI bus. This
problem can be corrected by configuring the firmware to operate in forced
pci mode. Refer to b57diag for configuration instructions.