A computer architecture simulator is a

program Program, programme, programmer, or programming may refer to: Business and management * Program management, the process of managing several related projects * Time management * Program, a part of planning Arts and entertainment Audio * Progra ...

that simulates the

execution Capital punishment, also known as the death penalty, is the State (polity), state-sanctioned practice of deliberately killing a person as a punishment for an actual or supposed crime, usually following an authorized, rule-governed process to ...

computer architecture In computer engineering, 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, t ...

. Computer architecture simulators are used for the following purposes: * Lowering cost by evaluating hardware designs without building physical hardware systems. * Enabling access to unobtainable hardware. * Increasing the precision and volume of computer performance data. * Introducing abilities that are not normally possible on real hardware such as running code backwards when an error is detected or running in faster-than-

real time Real-time or real time describes various operations in computing or other processes that must guarantee response times within a specified time (deadline), usually a relatively short time. A real-time process is generally one that happens in defined ...

Categories

Computer architecture simulators can be classified into many different categories depending on the context. * Scope: Microarchitecture simulators model the

microprocessor A microprocessor is a computer processor where the data processing logic and control is included on a single integrated circuit, or a small number of integrated circuits. The microprocessor contains the arithmetic, logic, and control circu ...

and its components. Full-system simulators also model the processor, memory systems, and I/O devices. * Detail: Functional simulators, such as

instruction set simulator An instruction set simulator (ISS) is a simulation model, usually coded in a high-level programming language, which mimics the behavior of a mainframe or microprocessor by "reading" instructions and maintaining internal variables which represent t ...

s, achieve the same function as modeled components. They can be simulated faster if timing is not considered. Timing simulators are functional simulators that also reproduce timing. Timing simulators can be further categorized into digital cycle-accurate and analog sub-cycle simulators. * Workload: Trace-driven simulators (also called event-driven simulators) react to pre-recorded streams of instructions with some fixed input. Execution-driven simulators allow dynamic change of instructions to be executed depending on different input data.

Full-system simulators

A full-system simulator is execution-driven architecture simulation at such a level of detail that complete software stacks from real systems can run on the simulator without any modification. A full system simulator provides virtual hardware that is independent of the nature of the host computer. The full-system model typically includes

processor core 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 ...

peripheral device A peripheral or peripheral device is an auxiliary device used to put information into and get information out of a computer. The term ''peripheral device'' refers to all hardware components that are attached to a computer and are controlled by the ...

memories Memory is the faculty of the mind by which data or information is encoded, stored, and retrieved when needed. It is the retention of information over time for the purpose of influencing future action. If past events could not be remembered, ...

, interconnection buses, and

network Network, networking and networked may refer to: Science and technology * Network theory, the study of graphs as a representation of relations between discrete objects * Network science, an academic field that studies complex networks Mathematics ...

connections.

Emulator In computing, an emulator is Computer hardware, hardware or software that enables one computer system (called the ''host'') to behave like another computer system (called the ''guest''). An emulator typically enables the host system to run so ...

s are full system simulators that imitate obsolete hardware instead of under development hardware. The defining property of full-system simulation compared to an

is that the model allows real

device drivers In computing, a device driver is a computer program that operates or controls a particular type of device that is attached to a computer or automaton. A driver provides a software interface to hardware devices, enabling operating systems and ot ...

and

operating system An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs. Time-sharing operating systems schedule tasks for efficient use of the system and may also in ...

s to be run, not just single programs. Thus, full-system simulation makes it possible to simulate individual computers and networked computer nodes with all their

software Software is a set of computer programs and associated documentation and data. This is in contrast to hardware, from which the system is built and which actually performs the work. At the lowest programming level, executable code consists ...

, from network device drivers to operating systems,

network stack The protocol stack or network stack is an implementation of a computer networking protocol suite or protocol family. Some of these terms are used interchangeably but strictly speaking, the ''suite'' is the definition of the communication protoco ...

middleware Middleware is a type of computer software that provides services to software applications beyond those available from the operating system. It can be described as "software glue". Middleware makes it easier for software developers to implement co ...

server Server may refer to: Computing *Server (computing), a computer program or a device that provides functionality for other programs or devices, called clients Role * Waiting staff, those who work at a restaurant or a bar attending customers and su ...

s, and

application program Application may refer to: Mathematics and computing * Application software, computer software designed to help the user to perform specific tasks ** Application layer, an abstraction layer that specifies protocols and interface methods used in a ...

s. Full system simulation can speed the system development process by making it easier to detect, recreate and repair flaws. The use of

multi-core processor A multi-core processor is a microprocessor on a single integrated circuit with two or more separate processing units, called cores, each of which reads and executes program instructions. The instructions are ordinary CPU instructions (such a ...

s is driving the need for full system simulation, because it can be extremely difficult and time-consuming to recreate and debug errors without the controlled environment provided by virtual hardware. This also allows the software development to take place before the hardware is ready, thus helping to validate design decisions.

Cycle-accurate simulator

A cycle-accurate simulator is a computer program that simulates a

microarchitecture In computer engineering, microarchitecture, also called computer organization and sometimes abbreviated as µarch or uarch, is the way a given instruction set architecture (ISA) is implemented in a particular processor. A given ISA may be impl ...

on a cycle-by-cycle basis. In contrast an

simulates an

instruction set architecture In computer science, an instruction set architecture (ISA), also called computer architecture, is an abstract model of a computer. A device that executes instructions described by that ISA, such as a central processing unit (CPU), is called an ' ...

usually faster but not cycle-accurate to a specific implementation of this architecture; they are often used when emulating older hardware, where time precision is important for legacy reasons. Often, a cycle-accurate simulator is used when designing new microprocessorsthey can be tested, and benchmarked accurately (including running full operating system, or compilers) without actually building a physical chip, and easily change design many times to meet expected plan. Cycle-accurate simulators must ensure that all operations are executed in the proper virtual (or real if it is possible) timebranch prediction, cache misses, fetches, pipeline stalls, thread context switching, and many other subtle aspects of microprocessors.

References

External links

*The Archer virtual infrastructure for computer architecture simulation *{{cite web, url=http://www.mikrocodesimulator.de/index_eng.php , title=Mikrocodesimulator MikroSim 2010 , publisher=0/1-SimWare , access-date=2010-12-06 Simulation software Computer architecture

Categories

Full-system simulators

Cycle-accurate simulator

See also

References

External links