Pipeline (computing)

Computer simulation, one of the main cross-computing methodologies.

Set of data processing elements connected in series, where the output of one element is the input of the next one.

- Pipeline (computing)

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Arithmetic logic unit

Arithmetic logic unit is a combinational digital circuit that performs arithmetic and bitwise operations on integer binary numbers.

A symbolic representation of an ALU and its input and output signals, indicated by arrows pointing into or out of the ALU, respectively. Each arrow represents one or more signals. Control signals enter from the left and status signals exit on the right; data flows from top to bottom.
The combinational logic circuitry of the 74181 integrated circuit, which is a simple four-bit ALU

Calculation pipeline: a group of simple ALUs that calculates a square root in stages, with intermediate results passing through ALUs arranged like a factory production line. This circuit can accept new operands before finishing the previous ones and produces results as fast as the very complex ALU, though the results are delayed by the sum of the propagation delays of the ALU stages. For more information, see the article on instruction pipelining.

Instruction pipelining

Technique for implementing instruction-level parallelism within a single processor.

Generic 4-stage pipeline; the colored boxes represent instructions independent of each other
A bubble in cycle 3 delays execution.

Pipelining attempts to keep every part of the processor busy with some instruction by dividing incoming instructions into a series of sequential steps (the eponymous "pipeline") performed by different processor units with different parts of instructions processed in parallel.

Branch predictor

Digital circuit that tries to guess which way a branch will go before this is known definitively.

Example of 4-stage pipeline. The colored boxes represent instructions independent of each other.
Figure 2: State diagram of 2-bit saturating counter
Figure 3: Two-level adaptive branch predictor. Every entry in the pattern history table represents a 2-bit saturating counter of the type shown in figure 2.

Branch predictors play a critical role in achieving high performance in many modern pipelined microprocessor architectures such as x86.

Out-of-order execution

Paradigm used in most high-performance central processing units to make use of instruction cycles that would otherwise be wasted.

This computer motherboard used in a personal computer is the result of computer engineering efforts.

It separates the fetch and decode stages from the execute stage in a pipelined processor by using a buffer.

Program counter

Processor register that indicates where a computer is in its program sequence.

Front panel of an IBM 701 computer introduced in 1952. Lights in the middle display the contents of various registers. The instruction counter is at the lower left.

Pipelining, in which different hardware in the CPU executes different phases of multiple instructions simultaneously.

Computer architecture

Set of rules and methods that describe the functionality, organization, and implementation of computer systems.

Block diagram of a basic computer with uniprocessor CPU. Black lines indicate data flow, whereas red lines indicate control flow. Arrows indicate the direction of flow.

Performance is affected by a very wide range of design choices — for example, pipelining a processor usually makes latency worse, but makes throughput better.

Microprocessor

Computer processor where the data processing logic and control is included on a single integrated circuit, or a small number of integrated circuits.

Texas Instruments TMS1000
Intel 4004
Motorola 68000 (MC68000)
A modern 64 bit x86-64 processor (AMD Ryzen 5 2600, Based on Zen+, 2017)
AMD Ryzen 7 1800X (2016, based on Zen) processor in a AM4 socket on a motherboard
A block diagram of the architecture of the Z80 microprocessor, showing the arithmetic and logic section, register file, control logic section, and buffers to external address and data lines
Intel Core i9-9900K (2018, based on Coffee Lake)
The PICO1/GI250 chip introduced in 1971: It was designed by Pico Electronics (Glenrothes, Scotland) and manufactured by General Instrument of Hicksville NY.
The 4004 with cover removed (left) and as actually used (right)
First microprocessor by Intel, the 4004
Upper interconnect layers on an Intel 80486DX2 die
ABIT BP6 motherboard supported two Intel Celeron 366Mhz processors picture shows Zalman heatsinks.
Abit BP6 dual-socket Motherboard shown with Zalman Flower heatsinks.

This system contained "a 20-bit, pipelined, parallel multi-microprocessor".

Hardware register

That they also have special hardware-related functions beyond those of ordinary memory.

Hardware interfaces of a Laptop computer: Ethernet network socket (center), to the left a part of the VGA port, to the right (upper) a display port socket, to the right (lower) a USB 2.0 socket.

In addition to the "programmer-visible" registers that can be read and written with software, many chips have internal microarchitectural registers that are used for state machines and pipelining; for example, registered memory.

Operand forwarding

Computer simulation, one of the main cross-computing methodologies.

Operand forwarding (or data forwarding) is an optimization in pipelined CPUs to limit performance deficits which occur due to pipeline stalls.

Power10

Superscalar, multithreading, multi-core microprocessor family, based on the open source Power ISA, and announced in August 2020 at the Hot Chips conference; systems with Power10 CPUs.

Power10 SCM

Each execution slice can handle 20 instructions each, backed up by a shared 512-entry instruction table, and fed to 128-entry-wide (64 single-threaded) load queue and 80-entry (40 single-threaded) wide store queue.