Scalar processors are a class of
computer processor
In computing and computer science, a processor or processing unit is an electrical component (digital circuit) that performs operations on an external data source, usually memory or some other data stream. It typically takes the form of a micropr ...
s that process only one data item at a time. Typical data items include
integer
An integer is the number zero (), a positive natural number (, , , etc.) or a negative integer with a minus sign ( −1, −2, −3, etc.). The negative numbers are the additive inverses of the corresponding positive numbers. In the languag ...
s and
floating point number
In computing, floating-point arithmetic (FP) is arithmetic that represents real numbers approximately, using an integer with a fixed precision, called the significand, scaled by an integer exponent of a fixed base. For example, 12.345 can be r ...
s.
Classification
A scalar processor is classified as a single instruction, single data (
SISD SISD can refer to:
* Single instruction, single data, a computer processor architecture
* CCL5, an 8kDa protein also using the symbol SISD
* Sixteen-segment display
* Several school districts in Texas. See List of school districts in Texas - S
* S ...
) processor in
Flynn's taxonomy
Flynn's taxonomy is a classification of computer architectures, proposed by Michael J. Flynn in 1966 and extended in 1972. The classification system has stuck, and it has been used as a tool in design of modern processors and their functionalities ...
. The
Intel 486
The Intel 486, officially named i486 and also known as 80486, is a microprocessor. It is a higher-performance follow-up to the Intel 386. The i486 was introduced in 1989. It represents the fourth generation of binary compatible CPUs following the ...
is an example of a scalar processor. It is to be contrasted with a
vector processor
In computing, a vector processor or array processor is a central processing unit (CPU) that implements an instruction set where its instructions are designed to operate efficiently and effectively on large one-dimensional arrays of data calle ...
where a single instruction operates simultaneously on multiple data items (and thus is referred to as a single instruction, multiple data (
SIMD
Single instruction, multiple data (SIMD) is a type of parallel processing in Flynn's taxonomy. SIMD can be internal (part of the hardware design) and it can be directly accessible through an instruction set architecture (ISA), but it shoul ...
) processor).
The difference is analogous to the difference between
scalar and
vector
Vector most often refers to:
*Euclidean vector, a quantity with a magnitude and a direction
*Vector (epidemiology), an agent that carries and transmits an infectious pathogen into another living organism
Vector may also refer to:
Mathematic ...
arithmetic.
The term ''scalar'' in computing dates to the 1970 and 1980s when vector processors were first introduced. It was originally used to distinguish the older designs from the new vector processors.
Superscalar processor
A
superscalar processor (such as the
Intel P5
The Pentium (also referred to as P5, its microarchitecture, or i586) is a fifth generation, 32-bit x86 microprocessor that was introduced by Intel on March 22, 1993, as the very first CPU in the Pentium brand. It was instruction set compatible ...
) may execute more than one instruction during a clock cycle by simultaneously dispatching multiple instructions to redundant functional units on the processor. Each functional unit is not a separate CPU core but an execution resource within a single CPU such as an arithmetic logic unit, a bit shifter, or a multiplier.
The
Cortex-M7
The ARM Cortex-M is a group of 32-bit RISC ARM processor cores licensed by Arm Holdings. These cores are optimized for low-cost and energy-efficient integrated circuits, which have been embedded in tens of billions of consumer devices. Thou ...
, like many consumer
CPUs
A central processing unit (CPU), also called a central processor, main processor or just processor, is the electronic circuitry that executes instructions comprising a computer program. The CPU performs basic arithmetic, logic, controlling, and ...
today, is a superscalar processor.
Scalar data type
A scalar data type, or just scalar, is any non-
composite
Composite or compositing may refer to:
Materials
* Composite material, a material that is made from several different substances
** Metal matrix composite, composed of metal and other parts
** Cermet, a composite of ceramic and metallic materials
...
value
Value or values may refer to:
Ethics and social
* Value (ethics) wherein said concept may be construed as treating actions themselves as abstract objects, associating value to them
** Values (Western philosophy) expands the notion of value beyo ...
.
Generally, all basic
primitive data type
In computer science, primitive data types are a set of basic data types from which all other data types are constructed. Specifically it often refers to the limited set of data representations in use by a particular processor, which all compiled pr ...
s are considered scalar:
* The
boolean data type
In computer science, the Boolean (sometimes shortened to Bool) is a data type that has one of two possible values (usually denoted ''true'' and ''false'') which is intended to represent the two truth values of logic and Boolean algebra. It is named ...
(
bool)
* Numeric types (
int, the
floating point
In computing, floating-point arithmetic (FP) is arithmetic that represents real numbers approximately, using an integer with a fixed precision, called the significand, scaled by an integer exponent of a fixed base. For example, 12.345 can b ...
types
float and
double)
* Character types (
char and
string)
A
variable
Variable may refer to:
* Variable (computer science), a symbolic name associated with a value and whose associated value may be changed
* Variable (mathematics), a symbol that represents a quantity in a mathematical expression, as used in many ...
(that is, a named location containing a scalar data type) is sometimes referred to as a "scalar".
See also
*
Instruction pipeline
In computer engineering, instruction pipelining or ILP is a technique for implementing instruction-level parallelism within a single processor. Pipelining attempts to keep every part of the processor busy with some instruction by dividing inco ...
*
Parallel computing
References
Central processing unit
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