32-bit bus primarily found in Sun SPARCstations. SBus used to be on pretty much all SPARC workstations, but recently PCI has displaced it on the low-end. SBus has a peculiar physical connector; the cards connect parallel to the motherboard, allowing SBus to be conveniently used in pizzabox enclosures:
M = motherboard
C = SBUS Connector
|----| = SBUS card
The only disadvantage to this is that if you want to remove the lower card, the upper card has to be taken out and replaced afterwards. Sun has recently abandoned the pizzabox enclosure, though, obsoleting the nifty style of connector that Sbus uses. Now all that Sun produces are boring PC-like cases.