This section provides information about the SBus polling order and how to change it. Skip this section if you know the order in which the SBus devices are addressed, or if you do not want to change the current order.
Two-slot SPARCstation systems, such as the SPARCstation IPX and LX, have four SBus addresses: 0, 1, 2, and 3. SBus address 0 is located on the main logic board and is reserved for system use. SBus slots (SBus addresses) 1 and 2 are for customer-installable SBus cards. SBus slots 1 and 2 are the only physical slots. SBus address 3 is the frame buffer on the main logic board.
The SPARCstation 2 system has no on-board frame buffer. Slots 1, 2, and 3 in this system are used to install SBus cards.
There is also no on-board frame buffer on the SPARCstation 10 and SPARCstation 20 systems. SBus address f is reserved for the CPU and should always be the first address in the sbus-probe-list. In SPARCstation 10 and 20 systems, SBus address lines 0, 1, 2, and 3 are used for customer-installable SBus cards.
The polling order is determined by the sbus-probe-list parameter in the system OpenBoot(TM) PROM. For the SPARCstation 10 and 20 systems, you must begin with f. This parameter is set up to poll the slots in order from 0 to 3. You can change the order of slots 1, 2, and 3, but you must begin with slot 0.
For example, if you install a frame buffer card into an SBus slot in SPARCclassic(TM), SPARCstation IPX, and SPARCstation LX systems, the system looks first for the frame buffer at the SBus slot rather than on the on-board frame buffer. If it finds a frame buffer at an SBus slot, the system establishes the video connection at that slot and looks no further. To have the system look first at the on-board frame buffer, you have to change the polling order to 0, 3, 1, 2.
If you change the sbus-probe-list in a SPARCstation IPX or LX system and select 3 as the console device, make sure that a monitor is attached to the on-board frame buffer. Otherwise, the system will not recognize any other monitor regardless of polling order.
The procedure described in this section is for experienced SunOS(TM) software users only. If you have only one monitor or do not need to change the probe list, do not follow this procedure. Any changes made to the system information displayed after typing the eeprom command will alter the system configuration.
As superuser, type:
# eeprom sbus-probe-list=0xyz (or fwxyz for a SPARCstation 10 system)
where xyz or wxyz is the order of SBus slots to be probed.
For example, in a SPARCclassic, SPARCstation IPX, and SPARCstation LX configuration, 0312 would cause SBus slot 3 (on-board frame buffer) to be probed first. After slot 3 is probed, SBus slots 1 and 2 will be probed, respectively. Here is what you would type for this example
# eeprom sbus-probe-list=0312
The leftmost character, except 0, in eeprom sbus-probe-list indicates the device that will be probed first. This will be the console device, regardless of its physical location.
If you are using a SPARCstation 10 or 20 system, the leftmost character in sbus-probe-list will be f (not 0) which is reserved for the CPU.