IBM 7090 User Manual

Auxiliary Start and Reset
This jack accepts the auxiliary start and reset key. The key is on a long cable,
giving the customer engineer a means for starting and resetting the machine at
points other than the console.
Phone Jack
The phone jack, in conjunction with the phone jacks on the other units in the system,
provides a means of communication between customer engineers working at different
units.
16K/24K Mode Switch
This switch is used with the compatibility package. When it is in the 16K position,
16K core storage positions are available to the 704 program; in the 24K position, 8K
core storage positions are available to the 704 program.
DC On
The DC on switch controls the 400-cycle power supplied only to the 7151. Putting
the DC on switch in the off position will immediately remove all power to the console,
except the convenience outlets and the reset motor (operator's keys). All voltages
should be normal about ten seconds after turning this switch to the on position.
6.3.00 MARGINAL CHECK
The system biasing network can be useful to the customer engineer. The controls are
located on the marginal check console on the 7151. Any single gate or combination of
gates in any single module, or combination of modules, can be biased at the same time.
The only exception is the 7302 memory. This module is under control of only one key, A,
and the whole module will be biased when this key is pressed.
Each module has a key for selecting it, and each gate has a key with key A for gate
A, B for gate B,etc.
When biasing, all gates must be selected prior to varying the voltage. After the
voltage has been varied, another gate cannot be selected until returning to normal volt-
age. If gate A is being biased and it is decided to bias gate B instead, gate A MC relay
must be dropped out; therefore it will be necessary to take the MC voltage to normal
before selecting gate B. If this is not done, gate A MC relay will have a hold through
the B MC relay points. This means that both gates A and B would be biased instead of
gate B only, as desired.
It is also possible to vary the +30v and +60v in the 7302. These controls are also
located in the 7151, on the MC panel.
vVhen varying the different voltages, there are two meters to monitor the amount of
voltage being varied. One meter is for the +30 and +60 in the 7302, and one meter, for
the +6 and -12 for the rest of the system. The meters indicate what the voltage is if
the MC relays are picked and the points are properly adjusted. A periodic check of the
voltages, while biasing, should be made.
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IBM 7090 Specifications

General

Category	Mainframe Computer
Introduced	1959
Transistor-based	Yes
Word Length	36 bits
Add Time	4.8 microseconds
Memory	Core memory
Memory (words)	32, 768 words