Emulator
While emulation could, if taken to the extreme, go down to the atomic level, basing its output on a simulation of the actual circuitry from a virtual power source, this would be a highly unusual solution.
Sufficient emulation of some hardware platforms requires extreme accuracy, down to the level of individual clock cycles, undocumented features, unpredictable analog elements, and implementation bugs.
This is particularly the case with classic home computers such as the Commodore 64, whose software often depends on highly sophisticated low-level programming tricks invented by game programmers and the "demoscene".
[3] For example, while the Nintendo 64 graphic processor was fully programmable, most games used one of a few pre-made programs, which were mostly self-contained and communicated with the game via FIFO; therefore, many emulators do not emulate the graphic processor at all, but simply interpret the commands received from the CPU as the original program would.
The first functional simulator was written by Autonetics about 1960[citation needed] for testing assembly language programs for later execution in military computer D-17B.
This made it possible for flight programs to be written, executed, and tested before D-17B computer hardware had been built.
Examples of console emulators that have been released in the last few decades are: RPCS3, Dolphin, Cemu, PCSX2, PPSSPP, ZSNES, Citra, ePSXe, Project64, Visual Boy Advance, Nestopia, and Yuzu.
This led to an effort by console manufacturers to stop unofficial emulation, but consistent failures such as Sega v. Accolade 977 F.2d 1510 (9th Cir.
[7][better source needed] Under United States law, obtaining a dumped copy of the original machine's BIOS is legal under the ruling Lewis Galoob Toys, Inc. v. Nintendo of America, Inc., 964 F.2d 965 (9th Cir.
Some terminal emulation applications include Attachmate Reflection, IBM Personal Communications, and Micro Focus Rumba.
Even if the emulated computer does not feature an MMU, though, there are usually other factors that break the equivalence between logical and physical memory: many (if not most) architectures offer memory-mapped I/O; even those that do not often have a block of logical memory mapped to ROM, which means that the memory-array module must be discarded if the read-only nature of ROM is to be emulated.
The simplest form of a CPU simulator is an interpreter, which is a computer program that follows the execution flow of the emulated program code and, for every machine code instruction encountered, executes operations on the host processor that are semantically equivalent to the original instructions.
This can result in a performance advantage, since each I/O module can be tailored to the characteristics of the emulated device; designs based on a standard, unified I/O API can, however, rival such simpler models, if well thought-out, and they have the additional advantage of "automatically" providing a plug-in service through which third-party virtual devices can be used within the emulator.
Emulation focuses on recreating an original computer environment, which can be time-consuming and difficult to achieve, but valuable because of its ability to maintain a closer connection to the authenticity of the digital object, operating system, or even gaming platform.
[8] Emulation addresses the original hardware and software environment of the digital object, and recreates it on a current machine.
[9] The emulator allows the user to have access to any kind of application or operating system on a current platform, while the software runs as it did in its original environment.
[10] Jeffery Rothenberg, an early proponent of emulation as a digital preservation strategy states, "the ideal approach would provide a single extensible, long-term solution that can be designed once and for all and applied uniformly, automatically, and in organized synchrony (for example, at every refresh cycle) to all types of documents and media".
Artists such as Cory Arcangel specialize in resurrecting obsolete technologies in their artwork and recognize the importance of a decentralized and deinstitutionalized process for the preservation of digital culture.
In many cases, the goal of emulation in new media art is to preserve a digital medium so that it can be saved indefinitely and reproduced without error, so that there is no reliance on hardware that ages and becomes obsolete.
It eases the development process by providing the ability to detect, recreate and repair flaws in the design even before the system is actually built.
[14] It is particularly useful in the design of multi-core systems, where concurrency errors can be very difficult to detect and correct without the controlled environment provided by virtual hardware.
[15] This also allows the software development to take place before the hardware is ready,[16] thus helping to validate design decisions and give a little more control.
In 1963, when microcode was first used to speed up this simulation process, IBM engineers coined the term "emulator" to describe the concept.
