IBM 7090 User Manual

Multiple Step High and Low Speed
The following explanation is with reference to Section 3.12.00. With this switch in
the high position, the multiple step key on the operator's panel performs program steps,
one after another, every 24 ms. With the switch in the low position, program steps
are performed every 104 ms. The high-speed position is advantageous when stepping
through index loops.
B Cycle Controls
These switches allow the machine to operate normally when they are in the down
position. In the up position, they modify normal operation as follows:
Interrupt: Prevents the 7606 from obtaining a B cycle by interrupting
a CPU instruction.
Share: Prevents the 7606 access to core storage during CPU L cycles.
End Operation: Prevents the 7606 from taking a B cycle when a CPU instruction
ends operation.
The switches can be used if the customer engineer wants to test the end operation
procedure of obtaining a B cycle. The interrupt and share switches would then be put
in the up position. This prevents a B cycle from being started in any manner except
end operation. Any of these switches in the up position turns off the ready light.
Machine Cycle Key (F igure 6. 2 -4)
The machine cycle receptacle on the customer engineer's test panel accepts the
machine cycle key. This key is used to sequentially step through the basic machine
cycles I, E, and L. When the machine cycle key is inserted into the customer engi-
neer's panel and pressed, the machine cycle trigger and machine cycle gate trigger are
turned on at A-O. The machine cycle trigger turns off the MST and allows for the proper
cycle time. after which the MST is turned on again. The machine cycle gate does two
things. First, it allows only three shifts per cycle on a shift operation, and forces a
wait until the shift counter equals zero before ending operation in L time. Second, it is
used to hold up "manual 1 time cntl" to insure that the machine will use a full 1 cycle.
"Manual 1 time cntl" is AND'ed with the output of the master 1 time trigger (Systems
08.00.18.1). Thus, if "manual I time cntl" drops, I time is finished. Usually, turning
on the MST at 17 causes "manual 1 time cntl" to fall and stop 1 time at 17. This allows
the machine to finish with an instruction before the following instruction is brought in.
Normally, the go to 1 time trigger (Systems 08. 00. 12. 1) is turned off at 19, but because
there is no 19, it remains on. The all pulse is blocked from resetting the master I time
trigger (Systems 08.00.08.1) by "minus on not go to 1 time." Therefore, if we start
again, the MST is turned off at A6, bringing up "manual I time cntl" and starting the
cycle at 16.
To
insure getting a full I cycle when using the machine cycle key, the machine cycle
gate trigger holds up "manual 1 time cntl" in the OR circuit on Systems 04.20.10.1.
When the key is not in use, a plug (sent with the system) that shorts pins 1 and 3 must
be inserted.
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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