Each system can support up to 8 SBS controllers, numbered 0-7. Unfortunately, there are no distinguishing marks on the controllers themselves to let you know which is which. cratelocator is a Tcl/Tk script that helps you identify the crate controllers.
The cratelocator utility presents you with a set of radiobuttons. Select one to choose a VME crate controller. Click the button. cratelocator rapidly issues VME operations on the crate which causes the selected controller's Remote light to glow. When you have identified the controller either click the button and select repeat this process until all controllers have been identified, or click to exit.
Note that unless you add VME controllers to the system, or rearrange the Fiber optic cabling, VME bus controller numbers will not change from reboot to reboot.