An undocumented feature is an unintended or undocumented hardware operation, for example an undocumented instruction, or software feature found in computer hardware and software that is considered beneficial or useful. Sometimes the documentation is omitted through oversight, but undocumented features are sometimes not intended for use by end users, but left available for use by the vendor for software support and development. Also, some unintended operation of hardware or software that ends up being of utility to users is simply a bug, flaw or quirk.
Since the suppliers of the software usually consider the software documentation to constitute a contract for the behavior of the software, undocumented features are generally left unsupported and may be removed or changed at will and without notice to the users.
Undocumented or unsupported features are sometimes also called "not manufacturer supported" (NOMAS), a term coined by PPC Journal in the early 1980s. [1] [2] [3] [4] Some user-reported defects are viewed by software developers as working as expected, leading to the catchphrase "it's not a bug, it's a feature" (INABIAF) and its variations. [5]
Undocumented instructions, known as illegal opcodes, on the MOS Technology 6502 and its variants are sometimes used by programmers. These were removed in the WDC 65C02.
Video game and demoscene programmers have taken advantage of the unintended operation of computers' hardware to produce new effects or optimizations.[ citation needed ]
In 2019, researchers discovered that a manufacturer debugging mode, known as VISA, had an undocumented feature on Intel Platform Controller Hubs (PCHs), chipsets included on most Intel-based motherboards, which makes the mode accessible with a normal motherboard. [6] Since the chipset has direct memory access this is problematic for security reasons.
Undocumented features (for example, the ability to change the switch character in MS-DOS, usually to a hyphen) can be included for compatibility purposes (in this case with Unix utilities) or for future-expansion reasons. However; if the software provider changes their software strategy to better align with the business, the absence of documentation makes it easier to justify the feature's removal.
New versions of software might omit mention of old (possibly superseded) features in documentation but keep them implemented for users who've grown accustomed to them. [7]
In some cases, software bugs are referred to by developers either jokingly or conveniently as undocumented features. [5] [8] This usage may have been popularised in some of Microsoft's responses to bug reports for its first Word for Windows product, [9] but doesn't originate there. The oldest surviving reference on Usenet dates to 5 March 1984. [10] Between 1969 and 1972, Sandy Mathes, a systems programmer for PDP-8 software at Digital Equipment Corporation (DEC) in Maynard, MA, used the terms "bug" and "feature" in her reporting of test results to distinguish between undocumented actions of delivered software products that were unacceptable and tolerable, respectively. This usage may have been perpetuated. [11]
Undocumented features themselves have become a major feature of computer games. Developers often include various cheats and other special features ("easter eggs") that are not explained in the packaged material, but have become part of the "buzz" about the game on the Internet and among gamers. The undocumented features of foreign games are often elements that were not localized from their native language.
Closed source APIs can also have undocumented functions that are not generally known. These are sometimes used to gain a commercial advantage over third-party software by providing additional information or better performance to the application provider.
Amiga is a family of personal computers introduced by Commodore in 1985. The original model is one of a number of mid-1980s computers with 16- or 16/32-bit processors, 256 KB or more of RAM, mouse-based GUIs, and significantly improved graphics and audio compared to previous 8-bit systems. These systems include the Atari ST—released earlier the same year—as well as the Macintosh and Acorn Archimedes. Based on the Motorola 68000 microprocessor, the Amiga differs from its contemporaries through the inclusion of custom hardware to accelerate graphics and sound, including sprites and a blitter, and a pre-emptive multitasking operating system called AmigaOS.
In computing, BIOS is firmware used to provide runtime services for operating systems and programs and to perform hardware initialization during the booting process. The firmware comes pre-installed on the computer's motherboard.
Industry Standard Architecture (ISA) is the 16-bit internal bus of IBM PC/AT and similar computers based on the Intel 80286 and its immediate successors during the 1980s. The bus was (largely) backward compatible with the 8-bit bus of the 8088-based IBM PC, including the IBM PC/XT as well as IBM PC compatibles.
A network interface controller is a computer hardware component that connects a computer to a computer network.
In computing, a non-maskable interrupt (NMI) is a hardware interrupt that standard interrupt-masking techniques in the system cannot ignore. It typically occurs to signal attention for non-recoverable hardware errors. Some NMIs may be masked, but only by using proprietary methods specific to the particular NMI. With regard to SPARC, the non-maskable interrupt (NMI), despite having the highest priority among interrupts, can be prevented from occurring through the use of an interrupt mask.
American Megatrends International, LLC, doing business as AMI, is an international hardware and software company, specializing in PC hardware and firmware. The company was founded in 1985 by Pat Sarma and Subramonian Shankar. It is headquartered in Building 800 at 3095 Satellite Boulevard in unincorporated Gwinnett County, Georgia, United States, near the city of Duluth, and in the Atlanta metropolitan area.
Gigabyte Technology is a Taiwanese manufacturer and distributor of computer hardware.
The Intel Graphics Media Accelerator (GMA) is a series of integrated graphics processors introduced in 2004 by Intel, replacing the earlier Intel Extreme Graphics series and being succeeded by the Intel HD and Iris Graphics series.
System Management Mode is an operating mode of x86 central processor units (CPUs) in which all normal execution, including the operating system, is suspended. An alternate software system which usually resides in the computer's firmware, or a hardware-assisted debugger, is then executed with high privileges.
An illegal opcode, also called an unimplemented operation, unintended opcode or undocumented instruction, is an instruction to a CPU that is not mentioned in any official documentation released by the CPU's designer or manufacturer, which nevertheless has an effect. Illegal opcodes were common on older CPUs designed during the 1970s, such as the MOS Technology 6502, Intel 8086, and the Zilog Z80. On these older processors, many exist as a side effect of the wiring of transistors in the CPU, and usually combine functions of the CPU that were not intended to be combined. On old and modern processors, there are also instructions intentionally included in the processor by the manufacturer, but that are not documented in any official specification.
Intel vPro technology is an umbrella marketing term used by Intel for a large collection of computer hardware technologies, including VT-x, VT-d, Trusted Execution Technology (TXT), and Intel Active Management Technology (AMT). When the vPro brand was launched, it was identified primarily with AMT, thus some journalists still consider AMT to be the essence of vPro.
A hardware bug is a bug in computer hardware. It is the hardware counterpart of software bug, a defect in software. A bug is different from a glitch which describes an undesirable behavior as more quick, transient and repeated than constant, and different from a quirk which is a behavior that may be considered useful even though not intentionally designed.
Sandy Bridge is the codename for Intel's 32 nm microarchitecture used in the second generation of the Intel Core processors. The Sandy Bridge microarchitecture is the successor to Nehalem and Westmere microarchitecture. Intel demonstrated an A1 stepping Sandy Bridge processor in 2009 during Intel Developer Forum (IDF), and released first products based on the architecture in January 2011 under the Core brand.
Intel Active Management Technology (AMT) is hardware and firmware for remote out-of-band management of select business computers, running on the Intel Management Engine, a microprocessor subsystem not exposed to the user, intended for monitoring, maintenance, updating, and repairing systems. Out-of-band (OOB) or hardware-based management is different from software-based management and software management agents.
The HP Pavilion dv9000 was a model series of laptops manufactured by Hewlett-Packard Company that featured 16:10 17.0" diagonal displays.
The HP Pavilion dv1000 was a model series of laptops manufactured by Hewlett-Packard Company that featured 16:10 14.1" diagonal displays.
The Intel Management Engine (ME), also known as the Intel Manageability Engine, is an autonomous subsystem that has been incorporated in virtually all of Intel's processor chipsets since 2008. It is located in the Platform Controller Hub of modern Intel motherboards.
In digital computing, hardware security bugs are hardware bugs or flaws that create vulnerabilities affecting computer central processing units (CPUs), or other devices which incorporate programmable processors or logic and have direct memory access, which allow data to be read by a rogue process when such reading is not authorized. Such vulnerabilities are considered "catastrophic" by security analysts.
The information contained in this document is made available with the understanding that it is not supported by Hewlett-Packard. […] When you read this document you will quickly notice that there is no effort to explain to non-design team members how or what is going on. At the time of [development] there was no plan to do this. While this document may stimulate more questions than it answers that situation must be accepted "as is". See the NOMAS statement stamped below. This material is being made available to the user community through PPC because we believe that information in this form is better than none at all. PPC offers this information as a service to the community. […] NOMAS - NOt MAnufacturer Supported - recipient agrees NOT to contact manufacturer […](710 pages)
NOMAS Listings - PPC has selected listings of the HP-41 system, associated ROMs (HP-IL, […] etc.), and HP-75 system listings available on a NOt MAnufacturer Supported basis. These listings have been made available to the user community with the understanding that those receiving the listings not contact the manufacturer regarding them.