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Bus and Tag is an "IBM standard for a computer peripheral interface", and was commonly used to connect their mainframe computers to peripheral devices such as line printers, 
Bus and Tag cables are " daisy chained"; and one interface can attach up to eight peripheral control units. The last control unit in the chain must have a terminator plug. Each control unit can attach a maximum number of devices, "sixteen is a typical number." There is an architectural limit of 256 devices per channel, and initially a limitation of , later extended to , between the mainframe and the control unit. Bus and Tag channels handle data rates up to 4.5 MB per second. Only one device can transfer data at a time.
Bus and Tag architecture was also used by other computer manufacturers to attach IBM peripherals to their systems. It was later published by the US National Technical Information Service (NTIS) as FIPS PUB 60-1, ''I/O Channel Interface''.
Bus and Tag was introduced with
Bus and Tag is an "IBM standard for a computer peripheral interface", and was commonly used to connect their mainframe computers to peripheral devices such as line printers, disk storage
Disk storage (also sometimes called drive storage) is a general category of storage mechanisms where data is recorded by various electronic, magnetic, optical, or mechanical changes to a surface layer of one or more rotating disks. A disk drive is ...
, magnetic tape drives and IBM 3270
The IBM 3270 is a family of block oriented display and printer computer terminals introduced by IBM in 1971
and normally used to communicate with IBM mainframes. The 3270 was the successor to the IBM 2260 display terminal. Due to the text ...
display controllers. The technology uses two sets of thick, multi-connector copper cables, one set, carrying data, called the ''bus'', and the other set, carrying control information, called the ''tag''.
Bus and Tag cables are " daisy chained"; and one interface can attach up to eight peripheral control units. The last control unit in the chain must have a terminator plug. Each control unit can attach a maximum number of devices, "sixteen is a typical number." There is an architectural limit of 256 devices per channel, and initially a limitation of , later extended to , between the mainframe and the control unit. Bus and Tag channels handle data rates up to 4.5 MB per second. Only one device can transfer data at a time.
Bus and Tag architecture was also used by other computer manufacturers to attach IBM peripherals to their systems. It was later published by the US National Technical Information Service (NTIS) as FIPS PUB 60-1, ''I/O Channel Interface''.
Bus and Tag was introduced with System/360
The IBM System/360 (S/360) is a family of mainframe computer systems that was announced by IBM on April 7, 1964, and delivered between 1965 and 1978. It was the first family of computers designed to cover both commercial and scientific applica ...
in 1964, and was also used with System/370. With the introduction of serial, fiber optic ESCON in the 1990s Bus and Tag channels were re-christened "parallel channels", and were gradually superseded. "