IBM 709 General Information Manual page 33

Figure 67. Data Transmission,
IBM
704 System
program starts an input operation by defining the in-
put device and the receiving storage area. Processing
is delayed while any data are being moved in or out of
storage. One advantage to this method is the ease in
programming effort. The great disadvantage is the
tremendous waste of possible computing time (Fig-
ure 67).
The data synchronizers permit the 709 central
processing unit to perform a more independent role
in controlling the input and output than that of the
704 central processing unit. In the 709 system, the
central processing unit initiates and monitors
1-0
op-
erations but is not interrupted with the detail of rout-
ing the data (Figure 68) .
Each data synchronizer is composed of two com-
pletely separate and independent input-output chan-
nels. These two data channels provide for simultaneous
computing and transmission between the input-output
units and core storage. A data channel may be thought
of as a small computer having the responsibility for
controlling the quantity and destination of all data
transmitted between core storage and an input-output
unit. It also performs limited counting and testing
operations exclusively concerned with the transmis-
sion of data.
No restrictions exist on the type of transmission
being performed by a data channel. All channels
may be used for input, output, or for a combination
of input-output operations that will be concurrent
with calculation (Figure 69) .
The
IBM
766 Data Synchronizer, used with the 709
system, provides a powerful link between core storage
and the input-output devices. This new concept of
input-output control enables processing to be per-
formed simultaneously with reading and writing. One,
Input·
Device
709 System
Figure 68. Data Transmission,
IBM
709, 7090 Systems
!l2 IBM 709-7090
Core Storage
Printer
Central Processing Unit
Figure 69. Simultaneous Input, Calculation, and Output
two, or three data synchronizers can be used in the
system. Since each data synchronizer contains two
input-output data channels, one channel can be read-
ing from a tape while the other channel is writing on
another tape, printer, or card punch. At the same
time, processing may be executed in the central proc-
essing unit.
The
IBM
766 Data Synchronizer (Figure 70) pro-
vides for improved methods of input-output control
listed below. They can be summarized as the ability
to:
1. Use the record structure of other
IBM
input-
output devices. This provides for the use of
other
IBM
computer tapes with the 709 system
thus making it compatible with other systems.
2. Use any previous
IBM
computer coding as input
data.
3. Transfer input data to scattered core storage
locations without loss of programming time.
4. Ignore unwanted data in a record. If desired,
unwanted data may be skipped.
7090 System