IBM 7090 - Page 161

Cycle Time
The cycle time indicators indicate in which cycle the machine is currently operating:
I, E, L, or B time. Also, in connection with cycle time, is the "multiple error" indi-
cator. This lamp is on whenever the machine is trying to perform two different cycles
at the same time other than an L cycle and a B cycle, which is a normal share opera-
tion. Refer to Systems 08.00.17.1
Tally Counter
The tally counter differentiates between the L cycles of floating point instructions
and provides gating for their different operational steps. The tally counter is divided
into five steps. The lamps on the test panel indicate in which of the five steps the ma-
chine is currently operating. Refer to Systems 02.10.21. 1 and 02. 10.22.1.
T-2
Indicator T-2 signifies the condition of the T-2 trigger in floating add or subtract,
multiply, and floating divide. During floating add or subtract, T-2 is used to indicate
whether or not the multiplier quotient equals O. During floating divide, T-2 is turned
on if the quotient is greater than 2. T-2 is turned on at the beginning of a floating
multiply second step to gate second step operations. The T-2 trigger is found on
Systems 2. 10.38.1.
FP
The floating point (FP) lamp indicates the condition of the FP trigger on Systems
2. 10. 29. 1. The trigger is used to store certain conditions throughout the floating
point operations. The conditions that turn on this trigger and indicator are shown
in Figure 6.2-2.
9 Carry
This lamp indicates the condition of the 9 carry trigger on Systems 2.10.37.1.
The trigger is turned on whenever there is a carry from adder position 9.
9 Overflow
The 9 overflow lamp signifies the condition of the 9 overflow trigger on Systems
2.10.39.1. The trigger and lamp come on whenever AC 9=1 during an accumulator
left shift, or during a multiply add cycle when there is an adder 9 carry.
Q Carry
The Q carry lamp indicates the condition of the Q carry trigger on Systems
2.10.36.1. This trigger is turned on whenever there is a carry out of adder position
Q.
Master Stop
The master stop lamp is turned on whenever the master stop trigger on Systems
4.20.11.1 is turned on.
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