what is mean by Computer Architecture ?
In computer science, computer architecture is a description of the structure of a computer system made from component parts It can sometimes be a high-level description that ignores details of the implementation. At a more detailed level, the description may include the instruction set architecture design, microarchitecture design, logic design, and implementation.
what are the Subcategories in Architecture ?
- Instruction set architecture
- Microarchitecture
- Systems design
- Macroarchitecture
- Assembly instruction set architecture
- Programmer-visible macroarchitecture
- Microcode
- UISA
- Pin architecture
1.Instruction set architecture(ISA)
It defines the machine code that a processor reads and acts upon as well as the word size,
memory address modes, processor registers, and data type.
An instruction set architecture (ISA) is the interface between the computer's software and hardware and also can be viewed as the programmer's view of the machine. Computers do not understand high-level programming languages such as Java, C++, or most programming languages used. A processor only understands instructions encoded in some numerical fashion, usually as binary numbers. Software tools, such as compilers, translate those high level languages into instructions that the processor can understand.
2.Microarchitecture
We also known as "computer organization", this describes how a particular processor will
implement the ISA. The size of a computer's CPU cache for instance,
is an issue that generally has nothing to do with the ISA.
For example, x86-64 is the ISA used by most modern laptop and desktop computers. It is implemented by various microarchitectures, including those designed by Intel and AMD. Software that is compiled for the x86-64 ISA can run on any microarchitecture designed to use the x86-64 instruction set.
3.Systems design
includes all of the other hardware components within a computing system, such as data processing other than the CPU (e.g., direct memory access), virtualization, and multiprocessing.
There are other technologies in computer architecture. The following technologies are used in bigger companies like Intel, and were estimated in 2002 to count for 1% of all of computer architecture:
System Design is the process of designing the architecture, components, and interfaces for a system so that it meets the end-user requirements. System Design for tech interviews is something that can’t be ignored! Almost every IT giant whether it be Facebook, Amazon, Google, Apple or any other ask various questions based on System Design concepts such as scalability, load-balancing, caching, etc. in the interview. This specifically designed System Design tutorial will help you to learn and master System Design concepts in the most efficient way from basics to advanced level.
System design refers to the process of defining the architecture, modules, interfaces, data for a system to satisfy specified requirements. It is a multi-disciplinary field that involves trade-off analysis, balancing conflicting requirements, and making decisions about design choices that will impact the overall system.
4.Macroarchitecture
the "visible" parts, the contract between hardware and software. It is architectural layers more abstract than microarchitecture For example: branch instructions.
5.Assembly instruction set architecture
A smart assembler may convert an abstract assembly language common to a group of machines into slightly different machine language for different implementations.
An Instruction Set Architecture (ISA) is part of the abstract model of a computer that defines how the CPU is controlled by the software. The ISA acts as an interface between the hardware and the software, specifying both what the processor is capable of doing as well as how it gets done.
The ISA provides the only way through which a user is able to interact with the hardware. It can be viewed as a programm
6.Programmer-visible macroarchitecture
higher-level language tools such as compilers may define a consistent interface or contract to programmers using them, abstracting differences between underlying ISA, UISA, and microarchitectures. For example, the C, C++, or Java standards
define different programmer-visible macroarchitectures..
For computers no matter how large or how small, “program visible” usually means the features of the hardware that are exposed to software, such as instructions, registers, memory maps, etc… also referred to as the ISA (Instruction Set Architecture). In other words, all the aspects of the processor that can be seen, controlled and modified by software written by users of the system.
An ISA can be implemented in multiple ways, reflecting different design trade-offs in cost, complexity, performance and reliability. The ISA concept originates from IBM’s System/360, which was the first computer architecture to be designed as a “family” as opposed to just one computer
7.Microcode
microcode is software that translates instructions to run on a chip. It acts like a wrapper around the hardware, presenting a preferred version of the hardware's instruction set interface. This instruction translation facility gives chip designers
flexible options: E.g. 1. A new improved version of the chip can use microcode to present the exact same instruction set as the old chip version,
so all software targeting that instruction set will run on the new chip without needing changes. E.g. 2. Microcode can present a variety of instruction sets for the same underlying chip,
allowing it to run a wider variety of software.
8.UISA
User Instruction Set Architecture, refers to one of three subsets of the RISC CPU instructions provided by PowerPC RISC Processors.
The UISA subset, are those RISC instructions of interest to application developers. The other two subsets are VEA (Virtual Environment Architecture) instructions used by virtualization system developers, and OEA (Operating Environment Architecture) used by Operation System developers.
9.Pin architecture
The hardware functions that a microprocessor should provide to a hardware platform, e.g., the x86 pins A20M, FERR/IGNNE or FLUSH. Also, messages that the processor should emit so that external caches can be invalidated (emptied). Pin architecture functions are more flexible than ISA functions because external hardware can adapt to new encodings, or change from a pin to a message. The term "architecture" fits, because the functions must be provided for compatible systems, even if the detailed method changes.
Histroy
The first documented computer architecture was in the correspondence between Charles Babbage and Ada Lovelace, describing the analytical engine. While building the computer Z1 in 1936, Konrad Zuse described in two patent applications for his future projects that machine instructions could be stored in the same storage used for data, i.e., the stored-program concept. Two other early and important examples are:
- John von Neumann's 1945 paper, First Draft of a Report on the EDVAC, which described an organization of logical elements;
- Alan Turing's more detailed Proposed Electronic Calculator for the Automatic Computing Engine, also 1945 and which cited John von Neumann's paper
Goals
The exact form of a computer system depends on the constraints and goals. Computer architectures usually trade off standards, power versus performance, cost, memory capacity, latency (latency is the amount of time that it takes for information from one node to travel to the source) and throughput. Sometimes other considerations, such as features, size, weight, reliability, and expandability are also factors. The most common scheme does an in-depth power analysis and figures out how to keep power consumption low while maintaining adequate performance.
For example, pipelining a processor usually makes latency worse, but makes throughput better. Computers that control machinery usually need low interrupt latencies. These computers operate in a real-time environment and fail if an operation is not completed in a specified amount of time. For example, computer-controlled anti-lock brakes must begin braking within a predictable and limited time period after the brake pedal is sensed or else failure of the brake will occur.
Power efficiency
Power efficiency is another important measurement in modern computers. Higher power efficiency can often be traded for lower speed or higher cost. The typical measurement when referring to power consumption in computer architecture is MIPS/W (millions of instructions per second per watt).
Modern circuits have less power required per transistor as the number of transistors per chip grows. This is because each transistor that is put in a new chip requires its own power supply and requires new pathways to be built to power it. However, the number of transistors per chip is starting to increase at a slower rate. Therefore, power efficiency is starting to become as important, if not more important than fitting more and more transistors into a single chip. Recent processor designs have shown this emphasis as they put more focus on power efficiency rather than cramming as many transistors into a single chip as possible. In the world of embedded computers, power efficiency has long been an important goal next to throughput and latency.
Shifts in market demand
Increases in clock frequency have grown more slowly over the past few years, compared to power reduction improvements. This has been driven by the end of Moore's Law and demand for longer battery life and reductions in size for mobile technology. This change in focus from higher clock rates to power consumption and miniaturization can be shown by the significant reductions in power consumption, as much as 50%, that were reported by Intel in their release of the Haswell microarchitecture; where they dropped their power consumption benchmark from 30 to 40 watts down to 10-20 watts. Comparing this to the processing speed increase of 3 GHz to 4 GHz (2002 to 2006) it can be seen that the focus in research and development is shifting away from clock frequency and moving towards consuming less power and taking up less space.
