The EBus is a low-speed (100MBit/sec) bus used on several models of Sun workstation. It is attached to the PCI bus, and the system's serial, parallel and audio hardware connects to it. Sun Ultra 30, 60 and 80 systems actually have an EBus slot, into which the sound card fits. This slot is about 30mm long, looking rather like the audio-modem riser slot found on some late-90s PCs. As far as I can tell from my research, no other devices were ever designed to fit the EBus slot.