1970 CNRZ Mécanographie-3-cliche Jean Weber

The IBM 2821 Control Unit attaches card readers and card punches, and

line printer A line printer prints one entire line of text before advancing to another line. Most early line printers were impact printers. Line printers are mostly associated with unit record equipment and the early days of digital computing, but the ...

s to the

IBM 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 ...

and

IBM System/370 The IBM System/370 (S/370) is a model range of IBM mainframe computers announced on June 30, 1970, as the successors to the System/360 family. The series mostly maintains backward compatibility with the S/360, allowing an easy migration path f ...

families of computers. The devices attached may be a combination of: * The

IBM 2540 The IBM 2540 is a punched-card computer peripheral manufactured by IBM Corporation for use of System/360 and later computer systems. The 2540 was designed by IBM's Data Processing Division in Rochester, Minnesota, and was introduced in 1965. The ...

card reader and card punch; * The

IBM 1403 The IBM 1403 line printer was introduced as part of the IBM 1401 computer in 1959 and had an especially long life in the IBM product line. Description The original model can print 600 lines of text per minute and can skip blank lines at up to ...

models 2, 3, 7 and N1 line printer; and * The

IBM 1404 The IBM 1403 line printer was introduced as part of the IBM 1401 computer in 1959 and had an especially long life in the IBM product line. Description The original model can print 600 lines of text per minute and can skip blank lines at up to ...

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 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 7000 series product lines. It ...

card reader/punch and the

and IBM 2201 printers. Six models of the IBM 2821 Control Unit were available, as follows: * Model 1 attaches one

and one

; * Model 2 attaches one

; * Model 3 attaches two or three

s; * Model 4 attaches one

and one

, but only on

models 25, 30, 40 and 50; * Model 5 attaches one

and two or three

s; and * Model 6 attaches one

. 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 software 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 Channel, channels, channeling, etc., may refer to: Geography * Channel (geography), in physical geography, a landform consisting of the outline (banks) of the path of a narrow body of water. Australia * Channel Country, region of outback Austral ...

. 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

* * * 2821 {{compu-hardware-stub