A computer architecture simulator is a

program Program (American English; also Commonwealth English in terms of computer programming and related activities) or programme (Commonwealth English in all other meanings), programmer, or programming may refer to: Business and management * Program m ...

that simulates the

execution Capital punishment, also known as the death penalty and formerly called judicial homicide, is the state-sanctioned killing of a person as punishment for actual or supposed misconduct. The sentence ordering that an offender be punished in ...

of computer architecture. 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.

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 (computing), processor for which the data processing logic and control is included on a single integrated circuit (IC), or a small number of ICs. The microprocessor contains the arithmetic, logic, a ...

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 (abstract), 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 ...

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 primary Processor (computing), processor in a given computer. Its electronic circuitry executes Instruction (computing), instructions ...

peripheral device A peripheral device, or simply peripheral, is an auxiliary hardware device that a computer uses to transfer information externally. A peripheral is a hardware component that is accessible to and controlled by a computer but is not a core compo ...

memories Memory is the faculty of the mind by which data or information is Encoding (memory), encoded, stored, and retrieved when needed. It is the retention of information over time for the purpose of influencing future Action (philosophy), action. I ...

, 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 sof ...

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 the context of an operating system, 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, enabli ...

and

operating system An operating system (OS) is system software that manages computer hardware and software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ...

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 consists of computer programs that instruct the Execution (computing), execution of a computer. Software also includes design documents and specifications. The history of software is closely tied to the development of digital comput ...

, 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 protoc ...

middleware Middleware is a type of computer software program 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 imple ...

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

s, and

application program Application software is any computer program that is intended for end-user use not operating, administering or programming the computer. An application (app, application program, software application) is any program that can be categorized as ...

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 (MCP) is a microprocessor on a single integrated circuit (IC) with two or more separate central processing units (CPUs), called ''cores'' to emphasize their multiplicity (for example, ''dual-core'' or ''quad-core''). Ea ...

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 electronics, computer science and 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 ...

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

simulates an

instruction set architecture In computer science, an instruction set architecture (ISA) is an abstract model that generally defines how software controls the CPU in a computer or a family of computers. A device or program that executes instructions described by that ISA, ...

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