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ANSWERS -- SYSTEM/360 AND INTERRUPTS
1.
a.
External
b.
Supervisor Call
c.
Program
d.
Machine
e.
I/O
2.
a.
Current PSW is the double-
being used by CPU to control
the execution of a sequence of
instructions.
There is only
one current
psw.
b.
Old PSW is the doubleword
placed in main storage as a
result of an interrupt.
There
are five locations reserved in
main storage, one for each
class of interrupt.
c.
New PSW is the doubleword
fetched from main storage as a
result of an interrupt.
It
then becomes the ·current· PSW.
Bits 40-63 of this doubleword
would switch the machine to a
new sequence of instructions.
3.
0063; there are 5 old PSW'S of 8
bytes each.
Each main storage
address refers to an individual
byte.
4.
0088
5.
0128; it uses the area of main
storage just above the area for new
PSW·s.
r-----~T--~---~------------,
6.
I
System 1
IAMWPI Interruption 1
lMask
1
1
1 Code
I
I
1
I
I
I
l ______
i ___
i_---i-~
__
--------J
o
7
12
1 IS
16
31
r---T----T------T-----------,
I
I
I
C
IProg. lInstructionl
I
L
J
C
IMask
I
Address
I
l ___ i -___
i ______
i~----------J
32
83
7.
Supervisor call interrupts and
those program interrupts not caused
by a.)
fixed point overflow, b.)
decimal overflow, c.)
exponent
underflow, or, d.)
significant.
The last two deal with floating
point arithmetic.
8.
0
9.
Only by an I/O or external inter-
rupt.
6-20
10.
Any interrupt
11.
The address of the channel and
1/0
unit
12.
The 8 bits in the Rl and R2 field
of the supervisor call instruction.
13.
32
33
r--~--'
11
01
L _____
J
t
ILC
14.
Privileged, Program Interrupt
15.
By issuing a ·LoadPSW· instruction
addressing the doubleword at loca-
tion 0120 (the old PSW for an I/O
interrupt) •
16.
a, c, e
17.
A.
byte from main storage
r----T--T--T--'
J
Op
1 I
I
I
t
Code 1121 B 1
t
D 11
l ____ i __
i __ i __ J
r-----------,
IMain storage 1
l ___________ J
o
7
r----T-----'
I
I
1
L ____
i _____
J
PSW
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