IBM 7090 User Manual

3. If, when reading, a data channel data register has not transmitted its
contents to storage by the time new information is to be loaded into it
from an output unit.
The 1-0 check lamp may be turned off by the execution of an lOT.
Read Light (White)
The ready lamp comes on after power comes up and remains on except when the ma-
chine is in automatic status, the continuous enter instruction switch is on, the 1-0 inter-
lock switch is in manual, or if any B-time control switch is on.
Automatic (Yellow)
The automatic lamp is on whenever the computer is executing instructions in the
automatic mode or whenever a data channel is in operation.
Console Power-On (Red)
The console power-on lamp is on whenever power is applied to the console.
Central Components Power Check (Yellow)
The central components power check comes on whenever a fuse or circuit breaker
opens in CPU frame 1 or 2, multiplexor, or core storage. It also lights when core
storage has improper oil temperature or low oil pressure.
1-0 Power Check (Yellow)
The 1-0 power check lamp is turned on whenever a fuse, an open thermal, or air-
flow failure is sensed in a data channel.
Power (Red)
The power indicator is turned on whenever DC power is up in core storage.
Marginal Check +6 (Yellow)
This indicator is on whenever the +6 supply marginal check variable autotransformer
is not in the home position.
Marginal Check -12 (Yellow)
This indicator is on whenever the -12 supply marginal check variable autotransformer
is not in the home position.
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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