Microarchitecture and Instruction Set Architecture Last Updated : 21 Jan, 2022 Comments Improve Suggest changes Like Article Like Report In this article, we look at what an Instruction Set Architecture (ISA) is and what is the difference between an 'ISA' and Microarchitecture. An ISA is defined as the design of a computer from the Programmer's Perspective. This basically means that an ISA describes the design of a Computer in terms of the basic operations it must support. The ISA is not concerned with the implementation-specific details of a computer. It is only concerned with the set or collection of basic operations the computer must support. For example, the AMD Athlon and the Core 2 Duo processors have entirely different implementations but they support more or less the same set of basic operations as defined in the x86 Instruction Set. Let us try to understand the Objectives of an ISA by taking the example of the MIPS ISA. MIPS is one of the most widely used ISAs in education due to its simplicity. The ISA defines the types of instructions to be supported by the processor. Based on the type of operations they perform MIPS Instructions are classified into 3 types: Arithmetic/Logic Instructions: These Instructions perform various Arithmetic & Logical operations on one or more operands.Data Transfer Instructions: These instructions are responsible for the transfer of instructions from memory to the processor registers and vice versa.Branch and Jump Instructions: These instructions are responsible for breaking the sequential flow of instructions and jumping to instructions at various other locations, this is necessary for the implementation of functions and conditional statements. The ISA defines the maximum length of each type of instruction. Since the MIPS is a 32 bit ISA, each instruction must be accommodated within 32 bits. The ISA defines the Instruction Format of each type of instruction. The Instruction Format determines how the entire instruction is encoded within 32 bits There are 3 types of Instruction Formats in the MIPS ISA: R-Instruction FormatI-Instruction FormatJ-Instruction Format If we look at the Abstraction Hierarchy: Figure - The Abstraction Hierarchy We note that the Microarchitectural level lies just below the ISA level and hence is concerned with the implementation of the basic operations to be supported by the Computer as defined by the ISA. Therefore we can say that the AMD Athlon and Core 2 Duo processors are based on the same ISA but have different microarchitectures with different performance and efficiencies. Now one may ask the need to distinguish between Microarchitecture and ISA? The answer to this lies in the need to standardize and maintain the compatibility of programs across different hardware implementations based on the same ISA. Making different machines compatible with the same set of basic instructions (The ISA) allows the same program to run smoothly on many different machines thereby making it easier for the programmers to document and maintain code for many different machines simultaneously and efficiently. This Flexibility is the reason we first define an ISA and then design different microarchitectures complying with this ISA for implementing the machine. The design of a lower-level ISA is one of the major tasks in the study of Computer Architecture. Instruction Set ArchitectureMicroarchitectureThe ISA is responsible for defining the set of instructions to be supported by the processor. For example, some of the instructions defined by the ARMv7 ISA are given below.The Microarchitecture is more concerned with the lower level implementation of how the instructions are going to be executed and deals with concepts like Instruction Pipelining, Branch Prediction, Out of Order Execution.The Branch of Computer Architecture is more inclined towards the Analysis and Design of Instruction Set Architecture. For Example, Intel developed the x86 architecture, ARM developed the ARM architecture, & AMD developed the amd64 architecture. The RISC-V ISA developed by UC Berkeley is an example of an Open Source ISA.On the other hand, the Branch of Computer Organization is concerned with the implementation of a particular ISA deals with various hardware implementation techniques, i.e. is the Microarchitecture level. For Example, ARM licenses other companies like Qualcomm, Apple for using ARM ISA, but each of these companies have their own implementations of this ISA thereby making them different in performance and power efficiency. The Krait cores developed by Qualcomm have a different microarchitecture and the Apple A-series processors have a different microarchitecture. The x86 was developed by Intel, but we see that almost every year Intel comes up with a new generation of i-series processors. The x86 architecture on which most of the Intel Processors are based essentially remains the same across all these generations but, where they differ is in the underlying Microarchitecture. They differ in their implementation and hence are claimed to have improved Performance. These various Microarchitectures developed by Intel are codenamed as 'Nehalem', 'Sandybridge', 'Ivybridge', and so on. Therefore, in conclusion, we can say that different machines may be based on the same ISA but have different Microarchitectures. Comment More infoAdvertise with us Next Article Types of Program Control Instructions A ArnaMaity Follow Improve Article Tags : Computer Organization & Architecture Technical Scripter 2018 Similar Reads Computer Organization and Architecture Tutorial In this Computer Organization and Architecture Tutorial, you’ll learn all the basic to advanced concepts like pipelining, microprogrammed control, computer architecture, instruction design, and format. Computer Organization and Architecture is used to design computer systems. Computer architecture i 5 min read Basic Computer InstructionsWhat is a Computer?A computer is an electronic device that processes, stores, and executes instructions to perform tasks. 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The CPU receives this signal, suspends the current instructions it is exe 5 min read I/O Interface (Interrupt and DMA Mode)The method that is used to transfer information between internal storage and external I/O devices is known as I/O interface. The CPU is interfaced using special communication links by the peripherals connected to any computer system. These communication links are used to resolve the differences betw 6 min read Direct memory access with DMA controller 8257/8237Suppose any device which is connected to input-output port wants to transfer data to memory, first of all it will send input-output port address and control signal, input-output read to input-output port, then it will send memory address and memory write signal to memory where data has to be transfe 3 min read Computer Organization | Asynchronous input output synchronizationIntroduction : Asynchronous input/output (I/O) synchronization is a technique used in computer organization to manage the transfer of data between the central processing unit (CPU) and external devices. 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It also allows parallel processing between CPU and I/O operations. This parallelism is necessary to avoid the wastage of valuable CPU time when handling I/O devices whose speeds are much slower as compared to CPU. 5 min read MPU Communication in Computer OrganizationMPU communicates with the outside world with the help of some external devices which are known as Input/Output devices. The MPU accepts the binary data from input devices such as keyboard and analog/digital converters and sends data to output devices such as printers and LEDs. For performing this ta 4 min read Memory Mapped I/O and Isolated I/OCPU needs to communicate with the various memory and input-output devices (I/O). Data between the processor and these devices flow with the help of the system bus. There are three ways in which system bus can be allotted to them:Separate set of address, control and data bus to I/O and memory.Have co 5 min read Memory OrganizationIntroduction to memory and memory unitsMemory is required to save data and instructions. Memory is divided into cells, and they are stored in the storage space present in the computer. Every cell has its unique location/address. Memory is very essential for a computer as this is the way it becomes somewhat more similar to a human brain. 11 min read Memory Hierarchy Design and its CharacteristicsIn the Computer System Design, Memory Hierarchy is an enhancement to organize the memory such that it can minimize the access time. The Memory Hierarchy was developed based on a program behavior known as locality of references (same data or nearby data is likely to be accessed again and again). The 6 min read Register Allocations in Code GenerationRegisters are the fastest locations in the memory hierarchy. But unfortunately, this resource is limited. It comes under the most constrained resources of the target processor. Register allocation is an NP-complete problem. However, this problem can be reduced to graph coloring to achieve allocation 6 min read Cache MemoryCache memory is a special type of high-speed memory located close to the CPU in a computer. It stores frequently used data and instructions, So that the CPU can access them quickly, improving the overall speed and efficiency of the computer. It is a faster and smaller segment of memory whose access 7 min read Cache Organization | Set 1 (Introduction)Cache is close to CPU and faster than main memory. But at the same time is smaller than main memory. The cache organization is about mapping data in memory to a location in cache. A Simple Solution: One way to go about this mapping is to consider last few bits of long memory address to find small ca 3 min read Multilevel Cache OrganisationCache is a type of random access memory (RAM) used by the CPU to reduce the average time required to access data from memory. Multilevel caches are one of the techniques used to improve cache performance by reducing the miss penalty. The miss penalty refers to the additional time needed to retrieve 6 min read Difference between RAM and ROMMemory is an important part of the Computer which is responsible for storing data and information on a temporary or permanent basis. Memory can be classified into two broad categories: Primary Memory Secondary Memory What is Primary Memory? Primary Memory is a type of Computer Memory that the Prepro 7 min read Difference Between CPU Cache and TLBThe CPU Cache and Translation Lookaside Buffer (TLB) are two important microprocessor hardware components that improve system performance, although they have distinct functions. Even though some people may refer to TLB as a kind of cache, it's important to recognize the different functions they serv 4 min read Introduction to Solid-State Drive (SSD)A Solid-State Drive (SSD) is a non-volatile storage device that stores data without using any moving parts, unlike traditional Hard Disk Drives (HDDs), which have spinning disks and mechanical read/write heads. Because of this, SSDs are much faster, more durable, and quieter than HDDs. They load fil 7 min read Read and Write operations in MemoryA memory unit stores binary information in groups of bits called words. Data input lines provide the information to be stored into the memory, Data output lines carry the information out from the memory. The control lines Read and write specifies the direction of transfer of data. Basically, in the 3 min read PipeliningInstruction Level ParallelismInstruction Level Parallelism (ILP) is used to refer to the architecture in which multiple operations can be performed parallelly in a particular process, with its own set of resources - address space, registers, identifiers, state, and program counters. It refers to the compiler design techniques a 5 min read Computer Organization and Architecture | Pipelining | Set 1 (Execution, Stages and Throughput)Pipelining is a technique used in modern processors to improve performance by executing multiple instructions simultaneously. It breaks down the execution of instructions into several stages, where each stage completes a part of the instruction. These stages can overlap, allowing the processor to wo 9 min read Computer Organization and Architecture | Pipelining | Set 3 (Types and Stalling)Please see Set 1 for Execution, Stages and Performance (Throughput) and Set 2 for Dependencies and Data Hazard. Types of pipeline Uniform delay pipeline In this type of pipeline, all the stages will take same time to complete an operation. In uniform delay pipeline, Cycle Time (Tp) = Stage Delay If 3 min read Computer Organization and Architecture | Pipelining | Set 2 (Dependencies and Data Hazard)Please see Set 1 for Execution, Stages and Performance (Throughput) and Set 3 for Types of Pipeline and Stalling. Dependencies in a pipelined processor There are mainly three types of dependencies possible in a pipelined processor. These are : 1) Structural Dependency 2) Control Dependency 3) Data D 6 min read Last Minute Notes Computer Organization Table of ContentBasic TerminologyInstruction Set and Addressing ModesInstruction Design and FormatControl UnitMemory Organization I/O InterfacePipeliningIEEE Standard 754 Floating Point NumbersBasic TerminologyControl Unit - A control unit (CU) handles all processor control signals. It directs all i 15+ min read COA GATE PYQ's AND COA QuizGATE CS PreparationPreparing for the GATE exam can be straightforward if you know the right steps to take. This brief GATE CSE Preparation Guide will help you get started and stay on track as you prepare for one of the most important exams for admissions into IITs, NITs and other government colleges.Let's get started: 3 min read Like