The IBM 2821 Control Unit attaches
card readers and card punches, and
line printer
A line printer Printer (computing), prints one entire line of text before advancing to another line. Most early line printers were
printer (computing)#Impact printers, impact printers.
Line printers are mostly associated with unit record eq ...
s to the
IBM System/360
The IBM System/360 (S/360) is a family of mainframe computer systems announced by IBM on April 7, 1964, and delivered between 1965 and 1978. System/360 was the first family of computers designed to cover both commercial and scientific applicati ...
and
IBM System/370
The IBM System/370 (S/370) is a range of IBM mainframe computers announced as the successors to the IBM System/360, System/360 family on June 30, 1970. The series mostly maintains backward compatibility with the S/360, allowing an easy migrati ...
families of computers.
The devices attached may be a combination of:
* The
IBM 2540 card reader and card punch;
* The
IBM 1403 models 2, 3, 7 and N1 line printer; and
* The
IBM 1404 model 2 line printer and bill feed printer.
The 2821 was originally advertised—in 1964, before System/360 shipped—as a controller for the
IBM 1402
The IBM 1402 was a high-speed Punched card reader, card reader/punch introduced on October 5, 1959 as a peripheral input/output device for the IBM 1401 computer. It was later used with other computers of the IBM 1400 series and IBM 700/7000 se ...
card reader/punch and the
IBM 1403 and
IBM 2201 printers.
Six models of the IBM 2821 Control Unit were available, as follows:
* Model 1 attaches one
IBM 2540 and one
IBM 1403;
* Model 2 attaches one
IBM 1403;
* Model 3 attaches two or three
IBM 1403s;
* Model 4 attaches one
IBM 2540 and one
IBM 1404, but only on
IBM System/360
The IBM System/360 (S/360) is a family of mainframe computer systems announced by IBM on April 7, 1964, and delivered between 1965 and 1978. System/360 was the first family of computers designed to cover both commercial and scientific applicati ...
models 25, 30, 40 and 50;
* Model 5 attaches one
IBM 2540 and two or three
IBM 1403s; and
* Model 6 attaches one
IBM 2540.
The 2821 is fully
buffered, that is it has buffers large enough to hold an entire card to punch, an entire card read, or an entire print line for each attached device. This frees the channel from having to meet the peripheral devices' tight timing requirements.
The control unit can be connected to either a
byte multiplexer channel or a
selector channel. It is made up of logically independent control units, but takes up only one of the eight control unit slots which can be connected to a
channel.
A two-channel switch is available, allowing the control unit to be connected to two channels, on one or two computer systems, controlled by manual switches or by programming.
The circuitry in the 2821 is largely older-technology
IBM SMS, unlike much of the System/360 line, but later revisions were partially implemented in
SLT or MST. As logic became cheaper, the functions of the 2821 were increasingly moved inboard to the central processor or outboard to the individual device. The 2821 was withdrawn from marketing in the United States in 1985.
References
External links
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2821
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