UPA Probing

Sun Enterprise 250 servers, like all UltraSPARC(TM)-based systems, are based on the high-speed Ultra Port Architecture (UPA) bus, a switched system bus that provides up to 32 port ID addresses (or slots) for high-speed motherboard devices like CPUs, I/O bridges, and frame buffers. The Enterprise 250 server provides up to three active ports for the following subsystems.

Table 1-1 UPA System Bus Ports

Device Type	UPA Slot	Physical Implementation
CPU	0-1	Two plug-in slots
UPA-PCI bridge	1f	Soldered on motherboard

The order of probing these three port IDs is not subject to user control; however, a list of ports can be excluded from probing via the upa-port-skip-list NVRAM variable. In the following example, the upa-port-skip-list variable is used to exclude CPU-1 from the UPA probe list.

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ok setenv upa-port-skip-list 1

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This capability lets you exclude a given device from probing (and subsequent use) by the system without physically removing the plug-in card. This can be useful in helping to isolate a failing card in a system experiencing transient failures.