Ibm 755 Tape Control; Multiplexor - IBM 709 General Information Manual

broadcast the picture from only one camera at a time;
a data channel must use only one
1-0
device at a time
although it is able to control several of them.
With as many as 48 tape units and three sets of
card machines controlled by the stored program, the
709 system can perform many jobs "on line" that were
formerly performed by auxiliary equipment. On line
means that the job is performed using the entire com-
puter system instead of using the "off line" auxiliary
equipment.
IBM 755 Tape Control
An
IBM
755 Tape Control (Figure 74) is attached
between every eight tape units and the appropriate
data channel. Several reasons why this is done are:
1. Tape signals must be amplified and analyzed to
be usable. Strong noise signals must be rejected,
and weak correct signals must be accepted.
2. Only six information bits can be written on tape
at one time. The tape control separates the 36-
bit word into six 6-bit characters and also gen-
erates a seventh checking bit for each character.
The characters are then delivered to the tape
recording head, one at a time. The process is
essentially reversed during tape reading. The
data transfer is shown in Figure 74.
3. A signal for the end of record, end of file, weak
or invalid character, or the physical end of tape
is also passed through the tape control to the
data channel.
Only the 704 and 709 systems use tape controls.
The
IBM
753 Tape Control is used with the 704 and
the
IBM
755 Tape Control is used with the 709 system.
The problem of asynchronous balance is resolved
in the 7090 system through a combination of two new
units that perform the simultaneous reading, writing,
and computing functions. These units are the
IBM
7606 Multiplexor and the
IBM
7607 Data Channel.
::,::
:
36 Bits
I
Figure 74. Data Transfer between Tape Control, Tape Unit, and
Data Channel
Figure 75.
IBM
7606 Multiplexor
Multiplexor
The
IBM
7606 Multiplexor (Figure 75) accomplishes
all of the data switching in the 7090 system. All input-
output components in the system must feed their data
through the multiplexor. Likewise, any data coming
from core storage must go first to the multiplexor and
then to the component.
Data flow in the 7090 system is shown in Figure 76.
The data flow path is from an input-output device to
the data channel to the multiplexor and then to core
storage.
Figure 76. Data Transmission,
IBM
7090 System
Input-Output Components 35