Platform Notes: Ultra 450 Workstation and Ultra Enterprise 450 Server

UPA Probing

Ultra 450 systems, like all UltraSPARC(TM) 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. While most Ultra systems employ only three or four active UPA ports, an Ultra 450 system provides up to nine active ports spread among the following subsystems.

Table 2-1 Active Ports


Device Type	UPA Slot	Physical Implementation
CPU	0-3	Four plug-in slots
UPA-PCI bridge	4,6,1f	Soldered on motherboard
UPA graphics frame buffer	1d, 1e	Two plug-in slots

The order of probing these nine 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 one of the UPA-PCI bridges and the primary UPA graphics card from the UPA probe list.

ok setenv upa-port-skip-list 4,1d

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.