A console emulator is a program that allows a computer or modern console (cross-console emulation) to emulate a video game console. Emulators are most often used to play older video games on personal computers and modern video game consoles, but they are also used to translate games into other languages, to modify (or hack) existing games, and in the development process of homebrewed demos and new games for older systems.
In April 1997, Bloodlust Software released version 0.2 of NESticle. An unannounced and unexpected release, NESticle shocked the nascent console emulation community with its ease of use and unrivaled compatibility with NES ROM images. NESticle arguably provided the catalyst with which console emulation took off: More and more users started experimenting with console emulation, and a new generation of emulators appeared following NESticle's lead. Bloodlust Software soon returned with Genecyst (emulating the Sega Genesis), and others released emulators like Snes9x and ZSNES (SNES). The rise of the console emulation community also opened the door to foreign video games and exposed North American gamers to Nintendo's censorship policies. This rapid growth in the development of emulators in turn fed the growth of the ROM hacking and fan-translation community. The release of projects such as RPGe's English language translation of Final Fantasy V drew even more users into the emulation scene.
Another legal consideration is that many emulators of fifth generation and newer consoles require a dumped copy of the original machine's BIOS in order to function. As this software is a copyrighted work and typically not accessible without specialised hardware, obtaining them generally requires the user to obtain the file illegally. Several emulators for platforms such as Game Boy Advance are capable of running without a BIOS file, using high-level emulation to simulate BIOS subroutines at a slight cost in emulation accuracy.
On the other hand, commercial developers have once again begun to turn to emulation as a means to repackage and reissue their older games on new consoles. Notable examples of this behavior include Square Enix's re-release of several older Final Fantasy titles on the PlayStation, Game Boy Advance, and DS; Sega's collections of Sonic the Hedgehog games. The most recent, and probably the most notable example is Nintendo's Virtual Console, which comes packaged with their seventh-generation system, the Wii and allows for emulation of NES, SNES, Nintendo 64, Sega Megadrive, TurboGrafx-16, MSX and Neo Geo computer games.
The Playstation 2 console uses the original PSX CPU as its primary sound hardware, and when an original Playstation title is inserted, the PSX CPU switches to full hardware emulation to power the original titles.
The Xbox 360 is not natively backwards-compatible with original Xbox games (due to the differing system architectures) and so backwards-compatibility is achieved through an emulator designed by Microsoft. The PlayStation 3 uses physical PSX hardware to play original Playstation titles. In US 60gb models, original PS2 graphics and CPU hardware was also present to run PS2 titles, however the PAL and later US models removed the PS2 CPU, replacing it with software emulation working alongside the video hardware to achieve partial hardware/software emulation. Further along, backwards compatibility with PS2 titles was completely removed when the PS2 graphics chip was removed and could not be emulated through software alone.