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SYSTEM COMPONENTS
5410 Processing Unit (CPU)
The IBM 5410 CPU (Figure 1-2) contains the facilities for
addressing storage, arithmetic and logical processing of
data, sequencing instructions, and controlling the transfer
of data between core storage and attached input/ output
devices. The basic unit of information is the byte which
represents one alphabetic, numeric, or special character.
In
arithmetic operations, a byte contains one numeric char-
acter and a zone. The low order byte contains the sign in
the zone portion. Bytes may be handled separately or
grouped together to form fields.
The CPU contains 8192 (8K) positions of core storage
which may be increased to 32,768 (32K) positions. The
storage locations are numbered consecutively
(0,
1,
2, .. )
_Each number corresponds to the address of an individual
byte.
The 5410 Model-C is the base system CPU. A02 through
A06 correspond to core size (Figure 1-1). Model D (disk
system) starts with Al3 (12K storage) and continues to
Al6.
The CPU core storage unit has a read/write cycle time of
1.2 us., with a data access time of 465 ns from the start of
Figure 1-2. IBM System/3
1-2
read. A calculation time is inserted between the read/write
time to provide a basic machine cycle (read/compute/write)
time of 1.52 us.
Addressing for CPU functions is maintained in local storage
registers (LSRs). These registers contain the core addresses
necessary for instruction sequencing as well as data manipu-
lation: both internally, and to and from 1/0 devices. In
addition, the LSRs are used
as
temporary storage for data
while the CPU is performing instructions.
Step-by-step data processing is controlled by registers (op
register,
Q
register, and condition register) which contain
the operation code for the instruction being performed and
the additional information required to execute the instruc-
tion.
Calculations within the CPU are performed in the arith-
metic and logical unit (ALU). All data to be processed
within the CPU is routed through the ALU which is capable
of performing the action required to arrive at the desired
result.
The CPU has direct control over all the 1/0 devices attached
to it. 1/0 operations are initiated and tested by program
instructions which determine what operation is performed
(read, write, etc.,) and which unit is to be used.
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