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.