or parallel bus interface). Its main difference is that it supports up to four processors on the same bus. Otherwise it is completely binary and electrically compatible with the standard Q-Bus, except for the physical layout of connectors. Cycle Types The Q-Bus supports 6 basic transaction types DATI Data in - master read - note no DATIB (not required) DATO Data out - master write DATOB Data out (byte) DATIO Data in/out DATIOB Data in/out (byte) IAK Interrupt Acknowledge Interfaces A wide range of interface cards are available for the Q-Bus. External links HP OpenVMS :: Q-Bus Hardware, HoffmanLabs DIY, The Lab - Q-Bus Beispielplatine, Selbstgebaute Q-BUS Platinen (Archive copye) DEC STD 160: LSI-11 Bus Specification PDP-11 Bus Handbook UNIBUS and LSI-11 Bus References DEC hardware Minicomputers Computer buses