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Photo of a burner shown as a blue colored box with eight slots on top, and a cartridge is in one of the slots.
Intelligent Systems ROM burner for the Nintendo DS

A ROM image, or ROM file, is a computer file which contains a copy of the data from a read-only memory chip, often from a video game cartridge, or used to contain a computer's firmware, or from an arcade game's main board. The term is frequently used in the context of emulation, whereby older games or firmware are copied to ROM files on modern computers and can, using a piece of software known as an emulator, be run on a different device than which they were designed for. ROM burners are used to copy ROM images to hardware, such as ROM cartridges, or ROM chips, for debugging and QA testing.

Creation

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Photo of a blue colored device with a large slot in front, and a cable is attached to the device
A ROM dumping device for the Game Boy Advance

ROMs can be copied from the read-only memory chips found in cartridge-based games and many arcade machines using a dedicated device in a process known as dumping. For most common home video game systems, these devices are widely available, examples being the Doctor V64, or the Retrode.

Dumping ROMs from arcade machines, which are highly customized PCBs, often requires individual setups for each machine along with a large amount of expertise.

Copy protection mechanisms

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While ROM images are often used as a means of preserving the history of computer games, they are also often used to facilitate the unauthorized copying and redistribution of modern games. Viewing this as potentially reducing sales of their products, many game companies have incorporated features into newer games which are designed to prevent copying, while still allowing the original game to be played. For instance, the GameCube uses non-standard 8 cm DVD-like optical media, which for a long time prevented games stored on those discs from being copied. It was not until a security hole was found in Phantasy Star Online Episode I & II that GameCube games could be successfully copied, using the GameCube itself to read the discs.

SNK also employed a method of copy prevention on their Neo Geo games, starting with The King of Fighters in 1999, which used an encryption algorithm on the graphics ROMs to prevent them from being played in an emulator. Many thought that this would mark the end of Neo Geo emulation. However, as early as 2000, hackers found a way to decrypt and dump the ROMs successfully, making them playable once again in a Neo Geo emulator.

Another company which used to employ methods of copy prevention on their arcade games was Capcom, which is known for its CPS-2 arcade board. This contained a heavy copy protection algorithm which was not broken until 7 years after the system's release in 1993. The original crack by the CPS2Shock Team was not a true emulation of the protection because it used XOR tables to bypass the original encryption and allow the game to play in an emulator. Their stated intent was to wait until CPS-2 games were no longer profitable to release the decryption method (three years after the last game release).[1] The full decryption algorithm was cracked in 2007 by Nicola Salmoria, Andreas Naive and Charles MacDonald of the MAME development team.

Another copy prevention technique used in cartridge-games was to have the game attempt to write to ROM. On an authentic cartridge this would do nothing; however, emulators would often allow the write to succeed. Pirate cartridges also often used writable chips instead of ROM. By reading the value back to see whether the write succeeded, the game could tell whether it was running from an authentic cartridge. Alternatively, the game may simply attempt to overwrite critical program instructions, which if successful renders it unplayable.

Some games, such as Game Boy games, also had other hardware such as memory bank controllers connected to the cartridge bus. The game would send data to this hardware by attempting to write it to specific areas of ROM; thus, if the ROM were writable, this process would corrupt data.

Capcom's latest arcade board is the CPS-3. This was resistant to emulation attempts until June 2007, when the encryption method was reverse-engineered by Andreas Naive. It is currently implemented by MAME and a variant of the CPS-2 emulator Nebula.

Uses

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Emulation

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Video game console emulators typically take ROM images as input files.

Software ROM

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ROM images are used when developing for embedded computers. Software which is being developed for embedded computers is often written to ROM files for testing on a standard computer before it is written to a ROM chip for use in the embedded systems.

Digital preservation

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The lifespan of digital media is rarely great. While black-and-white photographs may survive for a century or more, many digital media can become unreadable after only 10 years. This is beginning to become a problem as early computer systems may be presently fifty or sixty years old while early home video consoles may be almost forty years old. Due to this aging, there is a significant worry that many early computer and video games may not survive without being transferred to new media. So, those with an interest in preservation are actively seeking older arcade and video games and attempting to dump them to ROM images. When stored on standardized media such as CD-ROMs and DVD-ROMs, they can be copied to future media with significantly reduced effort.[2][3]

The trend towards mass digital distribution of ROM image files, while potentially damaging to copyright holders, may also have a positive effect on preservation. While over time many original ROM copies of older games may deteriorate, be broken or thrown away, a copy in file form may be distributed throughout the world, allowing games which would otherwise have been lost a greater chance of survival.[4]

Hacks and fan translations

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Main articles: Fan translation of video games and ROM hacking

Once games have been made available in ROM format, it is possible for users to make modifications. This may take the form of altering graphics, changing game levels, tweaking difficulty factor, or even translation into a language for which a game was not originally made available. Hacks can often take humorous forms, as is the case with a hack of the NES version of Mario Bros., titled Afro Mario Brothers, which features the famous brothers wearing Afro haircuts. The Metroid Redesign mod is a hack of Super Metroid that revamps the game and adds new objectives.

A large scene has developed to translate games into other languages. Many games receive a release in one part of the world, but not in another. For example, many role-playing video games released in Japan go unreleased in the West and East outside Japan. A group of fan translators will often translate the game themselves to meet demand for titles. For example, the 1995 game Tales of Phantasia was only officially released in Japan; DeJap Translations translated the game's on-screen text into English in 2001. Further to this, a project called Vocals of Phantasia was begun to translate the actual speech from the game. An official English version was not released until March 2006, some five years after the text translation was released. Another example was that of Mother 3, a Japan-only sequel to the cult-favorite Earthbound. In spite of massive fan response and several petitions for an English translation, the only response from Nintendo was that Mother 3 would be translated and released in Europe, which it never was. Instead, the fan website Starmen.net undertook a massive translation project and released the translated version of Mother 3 in October, 2008. The translation was praised by fans and even employees from Nintendo, Square Enix, and other industry professionals.

The Japanese N64 game Dōbutsu no Mori (Animal Forest) has also been translated into English. The game was originally only released on N64 in Japan, but it was ported to GameCube and renamed Animal Crossing.

Hacks may range from simple tweaks such as graphic fixes and cheats, to full-blown redesigns of the game, in effect creating an entirely new game using the original as a base.

Similar image types

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Image files derived from computer tape are known as tape images, while those derived from floppy disks and CD-ROMs (and other disk formats) are known as disk images. Images copied from optical media are also called ISO images, after one of the standard file systems for optical media, ISO 9660.

Creating images from other media is often considerably easier and can often be performed with off-the-shelf hardware. For example, the creation of tape images from games stored on magnetic tapes (from, for example, the Sinclair ZX80 computer) generally involves simply playing the magnetic tape using a standard audio tape player connected to the line-in of a PC sound card. This is then recorded to an audio file and transformed into a tape image file using another program. Likewise, many CD and DVD games may be copied using a standard PC CD/DVD drive.

See also

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  • Intel HEX (sometimes, files with the .ROM file extension do not contain data in binary but in Intel hex format)

References

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Revisions and contributorsEdit on WikipediaRead on Wikipedia

ROM image

View on Grokipedia
from Grokipedia
A ROM image, also known as a ROM file, is a digital file that serves as an exact binary copy of the data contained within a (ROM) chip from hardware devices such as cartridges, arcade motherboards, or computer . These files replicate the non-volatile contents of the original ROM, preserving the exact byte-for-byte structure without alteration, and are typically stored with a .rom file extension. Common in retro and gaming contexts, ROM images enable the reproduction of software or games originally designed for obsolete hardware. ROM images are created through a process called "dumping," where specialized hardware tools extract the directly from the physical ROM chip or the entire storage medium, such as a game cartridge or circuit board. This extraction method varies by device—for instance, video game consoles like the (NES) or require cartridge readers, while arcade systems involve chips from printed circuit boards. The resulting file maintains the original layout, including program code, , and sound assets, ensuring fidelity to the source material. Due to the technical nature of dumping, it often demands expertise to avoid corruption or incomplete captures. The primary application of ROM images is in software emulation, where they are loaded into programs to simulate the behavior of original hardware on modern computers, allowing users to run legacy operating systems, , or video games without the physical devices. For example, in arcade emulation via projects like MAME (Multiple Arcade Machine Emulator), ROM images are organized into "sets" comprising multiple files from specific chips, which the combines to recreate the full game environment accurately. Beyond gaming, ROM images support embedded systems development by providing test environments for updates and hardware prototyping. In efforts, ROM images play a crucial role in archiving software-dependent artifacts, particularly video games, by capturing irreplaceable data from aging media that may degrade or become unreadable on original hardware. Emulation paired with ROM images mitigates technological obsolescence, enabling long-term access to materials like classic titles from consoles or arcades when is unavailable. However, file formats can vary significantly by platform—such as merged single files for consoles versus multi-chip sets for arcades—requiring compatible emulators for proper functionality. This variability underscores the importance of standardized dumping practices in preservation workflows.

Overview

Definition

A ROM image is a that contains an exact of the stored on a (ROM) chip or cartridge, preserving the original bit-for-bit contents without alteration. This replication captures the immutable as it exists on the physical hardware, serving as a portable representation suitable for storage and analysis on computing devices. The key components of a ROM image consist of a raw dump, which typically includes program code for execution, graphics assets for visual rendering, and sound for audio output. In contrast to the physical ROM, a hardware-bound component integrated into devices like cartridges or circuit boards that requires specialized equipment to modify or duplicate, a ROM image exists as a software file that decouples the from its original medium, enabling broader accessibility and manipulation in digital environments. ROM images are commonly associated with contexts such as arcade machines, home video game consoles like the Nintendo Entertainment System (NES) and Sega Genesis, and early personal computers, where they replicate the firmware or game data essential to these systems. They also appear in embedded systems, where ROM images represent firmware that initializes and controls device operations. As a primary use case, ROM images facilitate software emulation, allowing modern hardware to simulate the behavior of legacy systems.

History

The practice of creating ROM images emerged in the among home computer enthusiasts who sought to preserve and back up software from erasable programmable read-only memory (EPROM) chips embedded in cartridges and hardware. Using specialized EPROM programmers, hobbyists would extract the binary data from these chips, often for personal archiving or to replicate functionality on compatible systems. In the , ROM image creation and sharing expanded through systems (BBS) and nascent communities, closely tied to the burgeoning console emulation scene. Early NES emulators, such as the Family Computer Emulator developed in 1990 for the FM Towns PC and iNES released in 1996, relied on dumped ROMs to simulate original hardware, fostering a culture of distribution via file-sharing networks. Milestones included the 1997 release of the first public ROM sets via tools like GoodTools, which standardized verification and organization of ROM collections for various platforms. The 2000s saw further standardization through projects like MAME, which debuted in 1997 and by the decade's midpoint had evolved into a comprehensive for arcade ROMs, promoting organized sets for preservation and play. This period also marked the rise of sites, where out-of-print video games, including ROM images, were archived and shared online, reflecting growing concerns over software obsolescence. From the onward, institutional efforts gained prominence, with organizations like the hosting extensive collections of ROM images for video games to safeguard . Legal advancements, such as the 2018 U.S. DMCA exemption, permitted libraries, archives, and museums to circumvent access controls on lawfully acquired video games for preservation purposes, provided they were not commercially available and lacked remote content dependencies. Concurrently, modern platforms like integrated retro game collections, allowing users to extract ROM images from purchased compilations for emulation. In October 2024, the U.S. Copyright Office denied proposals to expand the DMCA exemption to permit remote access to preserved video games in libraries and archives. Preservation efforts continued, with organizations like the Video Game History Foundation reporting progress in archiving and advocacy as of 2024. In July 2025, the Council on Library and Information Resources published a guide on emulation as a preservation method, emphasizing its role in maintaining access to legacy software.

Creation

Dumping Techniques

Dumping techniques for creating ROM images from primarily involve hardware-based methods to directly interface with memory chips, as these ensure accurate capture of the binary data stored in (ROM) types such as mask ROM or . Hardware approaches are favored for vintage game cartridges and embedded systems due to the non-volatile and fixed nature of the data, avoiding the need for runtime execution. In hardware-based dumping, the process begins with identifying the chip type, such as distinguishing mask ROM (non-erasable, factory-programmed) from (ultraviolet-erasable). For desoldering methods, the chip is removed from the circuit board using a or hot air station, then inserted into an EPROM programmer like the XGecu TL866II Plus, which connects via USB to a computer. The programmer's software detects the chip, reads its contents sector by sector—typically in 256-byte or 512-byte blocks—and outputs a raw binary file (.bin). To handle multi-chip cartridges, such as those in NES games with separate PRG (program) and CHR (character) ROMs, each chip is dumped individually; the resulting files are then combined using tools like nesromtool, which interleaves or concatenates them according to the system's mapper specifications to form a complete ROM image. Cartridge adapters simplify the process without , emulating the console's bus interface to access chips in . Devices like the Retrode connect via USB and support systems including NES, SNES, and ; users insert the cartridge, and the device exposes the ROM data as a file on the host computer, often requiring adapter plugins for specific formats. Similarly, the open-source INL Retro Dumper-Programmer handles NES, SNES, , and others by connecting to a PC ( preferred) and running scripts to read and save binary dumps, with manual header addition for iNES or similar formats post-dump. For logic analyzers, tools like Saleae capture address and data lines during console operation, reconstructing the ROM by logging reads, though this is less direct and more suited to verification. Software-based approaches apply to flashable ROMs in modern or reprogrammable devices, leveraging debug interfaces rather than direct chip access. Using (Joint Test Action Group) or SWD (Serial Wire Debug) ports, a like Segger J-Link connects to the device's pins, allowing software such as OpenOCD to halt execution, probe memory addresses, and extract flash contents into a . This method suits embedded systems with NAND or NOR flash, where commands like "dump_image" read sectors sequentially. Debug modes, activated via manufacturer-specific pins or bootloaders, enable similar extraction without hardware modification. Common challenges include bit errors from chip aging, poor connections, or electrical noise, which can flip individual bits and corrupt the dump; solutions involve performing multiple reads (e.g., 3–5 times) and comparing outputs with tools like or verification to identify and correct discrepancies by majority vote. Sector alignment issues arise in multi-chip or bank-switched setups, where incorrect address mapping leads to misordered data; this is resolved by referencing system documentation or using dumper software with predefined mapper profiles to ensure proper sequencing. Copy protection schemes can complicate reads by scrambling data or requiring specific timing, but general dumping focuses on raw capture before such obstacles.

Copy Protection Challenges

Copy protection in ROM images presents significant obstacles during the creation process, as manufacturers implemented various mechanisms to prevent unauthorized duplication of cartridges and . These protections often rely on hardware-specific features that verify authenticity before allowing access to the ROM data, complicating direct dumping techniques. Without proper circumvention, attempts to extract the ROM can result in failed reads, incomplete data extraction, or of anti-tampering measures that halt the process. Common types of protection include hardware locks, such as battery-backed RAM checks that monitor system and erase or corrupt data if unauthorized access is detected, and custom application-specific integrated circuits () embedded in cartridges to enforce proprietary handshakes with the console. schemes, like Sega's TradeMark Security System (TMSS) introduced in the early , require specific code sequences—such as writing the string "" to designated memory locations—to unlock execution, otherwise displaying a and disabling the game. These methods evolved from simpler 1980s checksum validations, where cartridges computed hashes during to detect modifications, to more sophisticated proprietary encodings that integrated console-specific authentication protocols. Historical examples illustrate the prevalence of these challenges in console gaming. Nintendo's Checking Integrated Circuit (CIC) lockout chip, deployed in the (NES) and (SNES) from the mid-1980s, uses a paired in both the console and cartridge to perform a one-way sequence; failure to match resets the CPU repeatedly, preventing ROM access. Overcoming these protections during ROM creation typically involves hardware modifications, such as physically clipping or replacing lockout chips like the CIC to disable authentication signals, or using software patches applied post-extraction to neutralize embedded checks. Specialized adapters, including the SNES EverDrive , facilitate bypassing by emulating legitimate hardware responses, allowing ROM data to be read and dumped without triggering protections, though compatibility varies with chip-specific games. In modern contexts, reverse-engineering tools like enable analysts to disassemble protected ROMs, identify authentication routines, and develop targeted patches for complete extraction. Failure to address copy protection adequately poses risks, including data corruption from interrupted reads or anti-tampering mechanisms that alter memory contents, leading to incomplete or unverifiable dumps. Such issues can manifest as bit errors in the extracted image, potentially propagating glitches into emulated gameplay or preservation archives if verification steps like checksum comparisons are skipped.

Applications

Emulation

ROM images serve as the foundational input for software emulation, enabling the replication of original hardware environments on modern systems. The core process involves loading the ROM data into an emulator's simulated , where it emulates the target system's CPU instructions, mapping, and peripheral devices such as graphics processors and sound chips. For instance, in cycle-accurate emulation, the emulator precisely replicates the timing of hardware operations to ensure compatibility with timing-sensitive software like certain arcade games, preventing glitches in audio or video output that could occur with less precise methods. Prominent exemplify this approach across different platforms. MAME, focused on arcade systems, achieves high accuracy by simulating hardware at a low level, loading ROM sets that include program code and graphics data to recreate original behaviors. , a cycle-accurate for the (NES), prioritizes faithful replication of the 6502 CPU and PPU (Picture Processing Unit), supporting ROMs up to 1MB in size for enhanced games. , for and consoles, employs both high-level emulation (HLE) for optimized performance on complex titles and low-level emulation (LLE) for precise hardware simulation, loading ISO-based ROM images to run games at resolutions far exceeding the originals. Emulation via ROM images offers significant advantages, including cross-platform accessibility that allows games to run on PCs, mobile devices, or consoles without the original hardware, reducing wear on aging physical components. Users benefit from enhancements such as effects for improved visuals, like scanline filters mimicking CRT displays, and netplay features for online multiplayer in originally single-player titles. These capabilities extend the lifespan of legacy software, supporting efforts by enabling archival playback on contemporary hardware. To function effectively, emulators require ROMs in compatible formats, often necessitating additional BIOS files—firmware dumps from the original console—for systems with proprietary boot processes. For example, PlayStation emulators like DuckStation demand BIOS files such as SCPH-5501 to initialize the MIPS CPU and handle CD-ROM interactions before loading game ROMs. Performance optimization is crucial for larger ROMs, such as (SNES) titles exceeding 1MB, where just-in-time () compilation dynamically translates emulated code into native machine instructions, boosting execution speed while maintaining compatibility.

Digital Preservation

ROM images play a crucial role in by safeguarding cultural artifacts from the inevitable degradation of physical hardware. Video game cartridges and other ROM-based media are susceptible to environmental factors such as heat, humidity, and , which can corrupt stored over time; for instance, battery leakage in cartridges often leads to acid that damages chips and renders the originals unreadable. By creating digital dumps, preservationists mitigate these risks, ensuring that software like classic arcade titles or console games remains accessible as a record of technological and cultural history. Methods for preserving ROM images involve meticulously dumping data from original hardware using specialized tools, such as readers or custom devices like the Sanni Cart Reader, to produce verified binary files. These dumps are then archived in public repositories, including the Internet Archive's extensive collections of emulatable software, such as the C64 Preservation Project, which hosts bit-accurate copies of vintage games. Similarly, the Software Preservation Society focuses on authentic, unaltered dumps of classic games to prevent bit rot and maintain the original production state, often relying on community-sourced originals for systems like the Commodore and ST. Checksums from standardized DAT files verify the integrity of these dumps, allowing for reliable storage and future playback via emulation. Standardization enhances the effectiveness of ROM preservation through projects like NOINTRO and TOSEC, which provide consistent naming conventions and comprehensive catalogs. NOINTRO maintains a database of the best available ROM copies, incorporating metadata such as CRC32 hashes for verification and region codes to distinguish variants, ensuring dumps are complete and free from alterations like intros or hacks. TOSEC, dedicated to retrocomputing preservation, catalogs software and with detailed naming that includes version, language, and media type, facilitating organized sets for long-term archiving. These standards promote across tools and repositories, reducing errors in collection management. Institutional efforts have advanced ROM preservation through legal and practical initiatives. Exemptions under the U.S. , first granted by the in 2018 and renewed in 2021, permitted eligible libraries, archives, and museums to circumvent technological protection measures on lawfully acquired video games for preservation purposes, provided server support had ended and access was restricted to on-site use. However, this exemption lapsed effective October 28, 2024, as it was not renewed in the subsequent triennial . The Video Game History Foundation, a , supports these activities by building specialized research libraries, recovering lost and prototypes, and advocating for broader access to preserved materials like early game builds. Corporate efforts have also advanced preservation; for example, established a dedicated team in 2022, which by March 2025 had preserved over 1,000 builds of PlayStation games, including alphas, betas, and releases. Despite these advances, challenges persist in ROM image preservation, including sourcing rare original hardware and media, which are increasingly scarce due to and prior discard. Managing duplicates requires rigorous hash verification to eliminate redundant or corrupted files, while format obsolescence threatens long-term accessibility as unsupported binary structures may become unreadable without ongoing migration efforts.

Modifications

Modifications to ROM images involve altering the binary data to enhance gameplay, add new features, or adapt content for different audiences, often through community-driven efforts. Common types include ROM hacks, which redesign elements like levels or mechanics, and fan translations, which convert text and from one language to another. For instance, ROM hacks may use level editors to create custom stages in games such as , while fan translations repatch Japanese-exclusive titles into English using dedicated tools and resources. Tools for these modifications typically include hex editors for direct byte-level changes, assemblers for injecting assembly code, and patch formats like IPS for applying non-destructive alterations to the original ROM. Hex editors such as allow precise editing of data structures, while assemblers enable advanced code modifications by recompiling snippets into the ROM's memory layout. IPS patches, created with utilities like Lunar IPS, store only the differences between the original and modified ROM, facilitating easy distribution and reversal without overwriting the base file. Notable examples demonstrate the creative potential of these techniques. , a ROM hack of developed by T. Takemoto, dramatically increases difficulty through redesigned levels and precise platforming challenges, serving as a benchmark for hardcore modifications. Similarly, certain ROM hacks incorporate or exploit (ACE) glitches to aid speedrunners by enabling custom warps or sequence breaks, as seen in tool-assisted speedrun demonstrations of the original . Communities played a central role in fostering these modifications, with platforms like Romhacking.net, which served as a major repository until August 2024. The site's archived collection includes approximately 8,520 ROM hacks and numerous fan translations, preserved on the for enthusiasts to access, while balancing the preservation of unmodified originals alongside modded variants. Technical constraints in ROM modifications arise from hardware limitations, such as , where larger ROMs divide data into swappable segments to exceed addressable memory bounds, requiring modders to carefully manage bank transitions to avoid corrupting code execution. Additionally, alterations can trigger errors—validation sums embedded in the ROM header that detect tampering—potentially preventing the modified from loading in emulators or original hardware; these are often resolved using specialized fixers like for SNES titles or rgbfix for ROMs. Copy protection schemes in some original ROMs further complicate modding by necessitating bypasses before unprotected dumps can be reliably altered.

Technical Aspects

File Formats

ROM images are stored in various file formats, ranging from simple raw binary dumps to more structured, system-specific containers that include metadata for compatibility with emulators. Raw formats provide unadorned copies of the ROM data without additional structure, making them versatile but requiring external information for proper interpretation. The .bin extension denotes a pure binary dump of the ROM chip's contents, commonly used across multiple systems as it preserves the exact data layout from the original hardware. Similarly, the .rom extension serves as a generic identifier for console ROM images, often applied to dumps from systems like or older handhelds, where the file lacks built-in headers and relies on naming conventions or accompanying documentation for context. System-specific formats incorporate headers or interleaving to encode hardware details directly in the file. For the (NES), the .nes extension uses the iNES format, which includes a 16-byte header followed by program ROM (PRG) and character ROM (CHR) data; the header specifies PRG size in 16 KB units (byte 4), CHR size in 8 KB units (byte 5), mapper number (bytes 6-7), mirroring configuration, and other flags like battery presence or system. The Mega Drive (also known as Genesis) employs the .smd format for ROM dumps, featuring a 512-byte header and interleaved data in 16 KB chunks—alternating even bytes from one ROM half with odd bytes from the other—to facilitate loading via devices like the Super Magic Drive copier; this format is often compressed with ZIP for distribution. Container formats bundle multiple files or compress single ROMs to manage larger sets, particularly for systems with segmented . The .zip format archives ROM images, widely used for arcade games where sets include separate files for program code, graphics, and sound data, allowing like MAME to load complete hardware simulations from one file. The .7z format offers superior compression ratios over ZIP and is similarly applied to multi-file ROM collections or individual dumps, though compatibility varies by —many support direct loading while others require extraction. For disc-based systems, the .iso format serves an archival role akin to ROM images by encapsulating read-only data tracks, though it is more commonly associated with optical media emulation. Headers and metadata in formats like iNES enhance usability by making files self-describing, embedding details such as mapper type (for memory mapping), PRG/CHR sizes, and hardware flags directly after the initial "NES" identifier bytes, which simplifies configuration and reduces errors in video mode or setup. These features provide advantages over raw dumps by enabling automatic detection of cartridge specifics, improving cross-platform portability, and supporting advanced emulation without manual intervention. Tools like RomCenter assist in standardizing ROM formats by auditing collections against databases, verifying integrity, renaming files to match preferred extensions (e.g., converting .bin to .smd), and rebuilding containers like ZIP archives to ensure consistency for emulation libraries.

Verification Methods

Verification of ROM images relies on hashing algorithms to ensure data integrity by detecting bit flips, corruption, or unauthorized modifications. Common methods include CRC32 for basic error detection, MD5 for more robust checks despite its cryptographic vulnerabilities, and SHA-1 as a preferred option for reliable verification of ROM contents. These hashes are computed from the ROM file and compared against predefined values to confirm accuracy. Redumping protocols enhance reliability by requiring multiple independent dumps of the same ROM source, followed by bit-by-bit comparisons using tools like hex editors or diff utilities to identify discrepancies. For instance, in disc-based systems, a dump achieves verified status only after corroboration from several sources, ensuring errors from hardware faults or media degradation are minimized. Specialized tools facilitate large-scale verification by scanning ROM collections against database files (DATs) that list expected hashes, sizes, and names. ClrMamePro, a widely used utility, audits ROMs for completeness and correctness, flagging mismatches or missing files based on DAT inputs from sources like MAME or console sets. Similarly, FinalBurn Neo (FBNeo) verifies arcade ROMs by matching against its specific ROMset versions, often using DAT files to confirm compatibility and integrity during emulation setup. Authenticity checks extend beyond hashes to validate internal structures, such as headers in ROM files. For NES ROMs, the iNES header is examined for the mapper ID (bits 4-7 of byte 6 and bits 0-3 of byte 7), which specifies the memory mapping hardware, and region flags (bit 0 of byte 7 for and other indicators for territorial variants). Cross-referencing these with hardware tests, like running the ROM on original consoles, further confirms legitimacy by observing behavior against known specifications. Best practices emphasize sourcing from verified repositories to distinguish "good" dumps—accurate, unaltered copies—from "bad" variants like pirated or corrupted files. Communities such as No-Intro provide DAT files listing hashes for their catalog of optimal ROMs, enabling users to rebuild collections excluding inferior or modified versions. GoodSets DATs similarly archive comprehensive hash databases, including alongside CRC32 and , to support thorough integrity audits.

Similar Image Types

ROM images share conceptual similarities with other types of digital dumps but differ in their origins from hardware, which enforces immutability. Disk images, commonly saved as .img or .iso files, capture the contents of floppy disks, hard drives, or optical media such as CDs and DVDs, often allowing read-write access when mounted as virtual drives. In contrast, ROM images derive from non-modifiable memory chips, preventing alterations and emphasizing archival fidelity over interactive use. Cartridge dumps for handheld consoles like the Game Boy produce full ROM images, typically in .gb format, encompassing the entire game program and assets from the cartridge's mask ROM or . These differ from partial SRAM dumps, which extract only battery-backed save data from volatile static RAM chips on the same cartridge, preserving user progress rather than the core software. Firmware images, such as or dumps, closely resemble ROM images in structure as non-volatile binary copies but serve as bootloaders to initialize hardware and operating systems, rather than delivering interactive game content. firmware, for instance, uses PE/COFF formats loaded into runtime or boot services memory, enabling persistent execution post-boot, unlike the fixed, game-specific payloads in ROM images. A core distinction lies in ROM images' non-volatile nature and fixed size, derived from hardware that retains data without power and maintains static dimensions (often megabytes per chip), setting them apart from volatile RAM dumps that evaporate on shutdown or compressed archives that reduce file size at the potential cost of exact bit-for-bit preservation. Overlaps occur in preservation workflows, where ROM-like data is extracted from larger disc images; for example, tools can pull assets or sub-ROMs from PlayStation 1 CD dumps in .bin/.cue format, converting multi-track optical data into focused binary files for emulation. This process highlights shared applications in emulation, where both ROM and disc images enable accurate software reproduction. ROM images, which replicate the data from video game cartridges or chips, are generally treated as reproductions of copyrighted software under law, potentially qualifying as derivative works if modifications are involved. In the United States, owners of original game copies may create personal archival backups under 17 U.S.C. § 117, which permits the owner of a to make an additional copy for archival purposes, provided the original is retained and the backup is destroyed if the original is transferred. However, video game ROMs often fall into a gray area due to debates over , where personal backups for non-commercial purposes might be defensible, but any distribution or public sharing constitutes direct . Key U.S. legislation includes the of 1998, which prohibits circumvention of technological protection measures (TPMs) on copyrighted works, complicating ROM creation even for owned games since many involve bypassing hardware protections. Exemptions granted by the U.S. Copyright Office provide limited relief for preservation; for instance, the 2015 rulemaking allowed libraries, archives, and museums to circumvent TPMs on video games for preservation purposes, without public access. This was expanded in 2018 to remove the prior limitation to games published before 2014, now covering all video games—including online and server-dependent ones—enabling eligible institutions to maintain playable copies for research and on their physical premises, with renewals in 2021 and 2024 maintaining this scope as of October 2024. Ethical concerns surrounding ROM images center on the tension between cultural preservation and the risk of facilitating , as unauthorized distribution undermines developers' revenue while archiving rare titles prevents their loss. A prominent case illustrating this dilemma is 's 2018 lawsuit against the operators of LoveROMs and LoveRETRO websites, where the ruled in favor of , resulting in a $12.1 million judgment for mass through ROM hosting and downloads. Regional differences highlight varying approaches; in the , Directive 2019/790 introduced mandatory exceptions allowing cultural heritage institutions to reproduce and make available works, including software, for preservation without commercial intent, extending protections to video games as part of digital . In contrast, Japanese copyright law under the Copyright Act of 1970 lacks a broad doctrine and provides narrower exceptions for private use, with companies like asserting that backup copies of their video games do not qualify under limited computer program provisions, leading to stricter enforcement against ROM creation and sharing. To navigate these issues responsibly, individuals should limit ROM use to private, non-distributed backups of personally owned originals, which can be created by extracting ROMs using dumping hardware such as the Retrode or Sanni Cart Reader; this is permitted in jurisdictions allowing private copies of lawfully acquired works, such as under Section 53 of Germany's Urheberrechtsgesetz (UrhG), provided the originals are retained. Individuals should also support official re-releases, such as Nintendo Switch Online's emulation of classic titles, which provide legal access while compensating rights holders. Digital preservation efforts by qualified institutions remain a legally supported pathway to safeguard ROM-based games without ethical conflicts.

References

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