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[[Image:ProActionReplay.jpg|200px|thumb|Action Replay cartridge for Sega Mega Drive.]]
'''Action Replay''' is the brand name of a series of devices created by [[Datel]], primarily used for changing the behavior of video games. Currently, Action Replay is available for the [[Nintendo GameCube]], [[Game Boy Advance]], [[PlayStation 2]], [[Xbox]], [[Nintendo DS]], and [[PlayStation Portable]] (PSP).

==Origin and history==
Action Replay has its roots in the Commodore 64 home computer. In its trademark red [[cartridge]], the Action Replay was one of the most popular ''turbo cartridges''; that is, cartridges that allowed faster disk and tape operations, allowing for example most of the disk operations to run 10 times faster. Another key point was it that it was also a ''freezer cartridge'', which meant it could stop the current program, save memory contents on tape or disk, and when this file was loaded again (on a C64 which need not have the cartridge installed), the program would continue from the exact same point. This allowed single-load games to be backed up and copied. The cartridge also included a lot of other utilities, like floppy disk file management and disk copying features.

Since then, there have been many revisions of the theme for various systems, but they have all, with some exceptions, retained the same feature found in C64 version, that is, the ability to examine memory locations and &mdash; more importantly — modify them. The exception to this rule are the [[Xbox]] and [[PlayStation Portable]] Action Replay devices, which are [[savestate]] transfer devices, as well as the Action Replay Max Duo for the Game Boy Advance and Nintendo DS (cheats work for Game Boy Advance games, yet only saves are used with Nintendo DS games).

==Method of Operation==
Action Replays capable of saving the system's state to tape or disk operated in broadly the same way. By attaching to the computer's memory bus (via the Zorro expansion slot on the Amiga) all memory access by the processor could be monitored. By keeping track of all writes to hardware registers (for example, to the video or sound hardware) the Action Replay could keep a complete copy of the state of all those registers in its own internal memory. This state could then be saved, along with the contents of the computer's RAM for later re-loading. By pressing a button on the Action Replay, an interrupt loaded a special monitor program from the Action Replay's ROM which could then be used to load, save and modify the computer's memory. It was even possible to alter CPU registers of the paused code, and later revisions included a complete disassembler. Cheating was possible by altering values stored in RAM.

A knob on the Amiga version of the Action Replay MKIII allowed games to be slowed down, to make them easier. This worked by intercepting vertical blank interrupts and running a wait loop until at least the next vertical blank. This did, however, have the limitation of only being able to reduce game speed by 50% or more (not, say, 10%).

The Action Replay was a formidable opponent for anyone trying to prevent their game code or graphics being ripped, or their game saved for later re-loading. One weakness was discovered in the Amiga version. It was possible to detect when the interrupt (hardware level 7, unmaskable) which the Action Replay used had been triggered, but only after the Action Replay monitor program had exited. At best the programmer could then choose to crash his program deliberately, making saved copies crash as well. However, it was possible to patch code which did this using the monitor program, so even that was not a total defence.

Later Action Replays which only supported cheat codes and had no monitor program worked by monitoring memory access for certain triggers, or by overwriting certain memory addresses at particular times (such as once per frame, or on a timer). On systems such as the Dreamcast, this could even be done entirely in software.

==Typical features==
General:

*With the Action Replay, users can obtain objects that are not obtainable during normal gameplay. Example: using the Action Replay to get three of the "Forbidden Four" NES games in ''Animal Crossing''.
*Action Replay allows users to have infinite amounts of limited resources, such as lives, time, money, or ammunition.
*Action Replay lets users access [[:Category:Levels|levels]] that are not normally available (most of these levels were usually used for [[beta testing]], or were removed from normal gameplay).
*Action Replay can activate programmer menus usually named "[[Debug mode|Debug]] Menus" that can be accessed with the correct parameter enabled that are normally unavailable to the player. Some functions/features that are usually included can be of great benefit to the player, such as access to Level Warps, Invincibility, various Test modes and unlocking various game features in an instant.
*Action Replay can download game saves and etc. if the user has internet access for his game console. (This doesn't apply to the GameCube.)

==Criticisms==
Datel, the maker of Action Replay, has received several criticisms from the gaming world over its products. One of the most popular complaints is the so-called "planned obsolescence" where codes for a just-released game require the most recent version of the cheat software. 

Datel as of now has encrypted the codes on the Action Replay for PS2, GC and GBA; this was meant to stop hackers from translating its codes for use in other cheating devices, but it prevents users from making their own codes for their games. It also prevents the creation of codes using a template. Cheat codes normally involve a memory address, a value, and sometimes a trigger that says when the code is activated (always on, on at the start, on after a certain button press); because of this, for some games it is possible to create a code template, and derive hundreds of codes by modifying the values. For example, in a role-playing game, one can use a code template and a table of values to create a code that will give any character, any piece of equipment in the game. By encrypting the codes, it is not possible to use such a template, and any code must be created and distributed by Datel; because of the sheer number of codes that can be created in this fashion, it is not plausible for Datel to release a list of codes with this versatility. A new Action Replay for the DS, which allows cheat codes (the previous Action Replay only managed game saves), uses unencrypted codes, and will have a trainer toolkit available to the public in the near future that allows users to create their own codes.

Sometimes, the codes for certain first-party games on the GameCube make it impossible to go further into the game with cheats activated (e.g. ''Pikmin'' and ''Star Fox Adventures''). Other times, cheats freeze the game in the first stage (e.g. if cheats are activated at the beginning of ''Super Mario Sunshine'' and ''Metroid Prime'', the game will freeze, and the system will have to be switched off). Also, in ''Pokémon'' games, advanced-generation ones especially, using the "Instant Win" code causes the glitch character "??????" to appear, usually resulting in a corrupted game. Nintendo does not license the Action Replays for its versions. That being said, Datel's website often indicates when a code should not be used.

A common infamous thing the PS2 Action Replay version does is corrupting [[memory cards]], leaving corrupt files on the card that cannot be deleted by the PS2. The Action Replay can, however, fix the memory card by formatting it, but the corrupted data cannot be restored.

Since the launch of the Nintendo DS with its Wi-Fi capabilities, Action Replay has allowed many Nintendo fans to don the mantel of "hacker." Action Replay users have succeeded in altering games in progress with other (often unknowing) player. While most of this breed of "hacker" does nothing malicious, many cases have arisen in which legitimate users have found their saved data irreparably altered or have been simply put off by the advanced levels of cheating within the Wi-Fi network.

==Versions for computers==
*Commodore 64
**Action Replay
**Action Replay II
**Action Replay III
**Action Replay IV (1988)
**Action Replay V  (1988)
**Action Replay VI (1989)

*Commodore Amiga
**Action Replay (A500 cart / A2000 CPU card)
**Action Replay (A1200 card)
**Action Replay Mk II (A500 cart / A2000 CPU card)
**Action Replay Mk III (A500 cart / A2000 CPU card) (1991)

*PC
**Action Replay PC (ISA card) (1994)

==Versions for video game consoles==
===8-bit era===
*Nintendo Entertainment System
**Pro Action Replay

*[[Sega Master System]]
**Pro Action Replay

===16-bit era===
*[[Sega Mega Drive/Genesis]]
**Action Replay
**Pro Action Replay
**Pro Action Replay 2

*Super NES
**Pro Action Replay
**Pro Action Replay MK2
**Pro Action Replay MK3

===32/64-bit era===
*[[Sega Saturn]]
**Pro Action Replay (also available with 4M RAM expansion)

*PlayStation
**Action Replay (1995)
**Pro Action Replay (1996)
**Action Replay CDX (1997)

*Nintendo 64
**Pro Action Replay (1999)
**N64 Equaliser

===6th generation era===
*[[Sega Dreamcast]]
**Action Replay CDX
*[[PlayStation 2]]
**Action Replay 2 (2000)
**Action Replay 2 V2 (2001)
**Action Replay MAX (2003, significantly updated in 2004)
**Action Replay MAX evo edition
*[[Xbox]]
**Action Replay (2002)
*[[Nintendo GameCube]]
**Action Replay (2003)
**Action Replay Max Evo (200X)

==Versions for handheld consoles==
*Game Boy
**Pro Action Replay
**Action Replay Online
**Action Replay Extreme
*[[Sega Game Gear]]
**Pro Action Replay
*Game Boy Color
**Pro Action Replay
*[[Game Boy Advance]]
**Action Replay (2001)
**Action Replay Duo (2005)
*[[Nintendo DS]]
**Action Replay Duo (2005)
**Action Replay DS (July 2006)
*[[PlayStation Portable]] (PSP)
**Action Replay MAX (2005)

==See also==
*[[GameShark]]
*[[Game Genie]]

==External links==
*[http://www.codejunkies.com/ CodeJunkies.com] &ndash; Official Action Replay website

{{MegaDrive}}

[[Category:Hardware]]