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computer jargon Jargon is the specialized terminology associated with a particular field or area of activity. Jargon is normally employed in a particular communicative context and may not be well understood outside that context. The context is usually a particu ...
, a killer poke is a method of inducing physical hardware damage on a machine or its
peripheral A peripheral or peripheral device is an auxiliary device used to put information into and get information out of a computer. The term ''peripheral device'' refers to all hardware components that are attached to a computer and are controlled by the ...
s by the insertion of invalid values, via, for example,
BASIC BASIC (Beginners' All-purpose Symbolic Instruction Code) is a family of general-purpose, high-level programming languages designed for ease of use. The original version was created by John G. Kemeny and Thomas E. Kurtz at Dartmouth College i ...
's POKE command, into a memory-mapped control
register Register or registration may refer to: Arts entertainment, and media Music * Register (music), the relative "height" or range of a note, melody, part, instrument, etc. * ''Register'', a 2017 album by Travis Miller * Registration (organ), the ...
. The term is typically used to describe a family of fairly well known tricks that can overload the
analog electronics Analogue electronics ( en-US, analog electronics) are electronic systems with a continuously variable signal, in contrast to digital electronics where signals usually take only two levels. The term "analogue" describes the proportional relat ...
in the CRT monitors of computers lacking hardware
sanity check A sanity check or sanity test is a basic test to quickly evaluate whether a claim or the result of a calculation can possibly be true. It is a simple check to see if the produced material is rational (that the material's creator was thinking ration ...
ing (notable examples being the IBM Portable and
Commodore PET The Commodore PET is a line of personal computers produced starting in 1977 by Commodore International. A single all-in-one case combines a MOS Technology 6502 microprocessor, Commodore BASIC in read-only memory, keyboard, monochrome monitor, an ...
.)


Specific examples


Zuse Z1/Z3

The Z1 (1938) and Z3 (1941) computers built by
Konrad Zuse Konrad Ernst Otto Zuse (; 22 June 1910 – 18 December 1995) was a German civil engineer, pioneering computer scientist, inventor and businessman. His greatest achievement was the world's first programmable computer; the functional program-c ...
contained illegal sequences of instructions which damaged the hardware if executed by accident.


Commodore PET

The
PET A pet, or companion animal, is an animal kept primarily for a person's company or entertainment rather than as a working animal, livestock, or a laboratory animal. Popular pets are often considered to have attractive appearances, intelligence, ...
-specific killer poke is connected to the architecture of that machine's video rasterizer circuits. In early PETs, writing a certain value to the memory address of a certain I/O register (POKE 59458,62) made the machine able to display text and graphics on the screen 106% faster. This was accomplished by disabling a “wait to print to screen” safeguard designed to reduce static/noise by preventing the shared VRAM from being read by the display at the same time as it was being written to by the CPU. With this safeguard disabled, graphics could appear on the screen twice as fast, but small bits of static would also appear. Despite the static, some games designed for early PETs included this POKE in their source code in order to benefit from the faster graphics. When the PET range was revamped with updated hardware, the video rasterizer circuits were redesigned to run at a faster speed and without the need for a “wait to print” safeguard. Thus, the old POKE trick no longer resulted in faster graphics. Instead, performing the old trick on the new hardware led to strange behavior by the new video chip, which could cause signal contention and possibly damage the PET's integrated CRT monitor. This is because the exact pin targeted by the POKE command used to control display timing, but in the upgraded video chip, that pin controlled the vertical sync. Thus, running the POKE on the newer hardware caused graphics to compress vertically, sometimes down to an extremely bright horizontal line. Fears that this anomaly might burn in to the display led to the nickname “killer poke,” however, it is not known to have ever caused any permanent damage to the monitor.


Commodore 1541 Disk Drive

The
Commodore 64 The Commodore 64, also known as the C64, is an 8-bit computing, 8-bit home computer introduced in January 1982 by Commodore International (first shown at the Consumer Electronics Show, January 7–10, 1982, in Las Vegas). It has been listed in ...
had an optional external 5-1/4" floppy drive. The
Commodore 1541 The Commodore 1541 (also known as the CBM 1541 and VIC-1541) is a floppy disk drive which was made by Commodore International for the Commodore 64 (C64), Commodore's most popular home computer. The best-known floppy disk drive for the C64, the ...
contained a 6502 microprocessor which was used to run
Commodore DOS Commodore DOS, also known as CBM DOS, is the disk operating system used with Commodore's 8-bit computers. Unlike most other DOSes, which are loaded from disk into the computer's own RAM and executed there, CBM DOS is executed internally in the d ...
and also to manage the drive mechanism. The drives stored data on 35 tracks (#0–34), and the stepper motor could be manually controlled through BASIC by PRINT#-ing "MEMORY-WRITE" commands to the drive (which correspond to the POKE command of BASIC, but write to the drive's internal memory and I/O registers, not those of the computer itself). If the drive was at either end of its range (track 0 or track 39) and it was commanded to continue moving, there was no software or firmware method to prevent drive damage. Continued "knocking" of the drive head against the stop would throw the mechanism out of alignment. The problem was exacerbated by
copy protection Copy protection, also known as content protection, copy prevention and copy restriction, describes measures to enforce copyright by preventing the reproduction of software, films, music, and other media. Copy protection is most commonly found o ...
techniques that used non-standard disk formats with unusual track counts. The
Commodore 1571 The Commodore 1571 is Commodore's high-end 5¼" floppy disk drive, announced in the summer of 1985. With its double-sided drive mechanism, it has the ability to use double-sided, double-density (DS/DD) floppy disks, storing a total of 360&nbs ...
had an optical head stop instead of a mechanical one.


TRS-80 Model III

The
TRS-80 Model III The TRS-80 Micro Computer System (TRS-80, later renamed the Model I to distinguish it from successors) is a desktop microcomputer launched in 1977 and sold by Tandy Corporation through their Radio Shack stores. The name is an abbreviation of ''T ...
had the ability to switch between a 32-character-wide display and a 64-character display. Doing so actuated a relay in the video hardware, accomplished by writing to a specific memory-mapped control register. Programs that repeatedly switched between 32- and 64-character modes at high speed (either on purpose or accidentally) could permanently damage the video hardware. While this is not a single "killer poke", it demonstrates a software
failure mode Failure causes are defects in design, process, quality, or part application, which are the underlying cause of a failure or which initiate a process which leads to failure. Where failure depends on the user of the product or process, then human er ...
that could permanently damage the hardware.


Cassette tape relay

The
TRS-80 Color Computer The RadioShack TRS-80 Color Computer, later marketed as the Tandy Color Computer and sometimes nicknamed the CoCo, is a line of home computers developed and sold by Tandy Corporation. Despite sharing a name with the earlier TRS-80, the Color Com ...
,
IBM PC The IBM Personal Computer (model 5150, commonly known as the IBM PC) is the first microcomputer released in the IBM PC model line and the basis for the IBM PC compatible de facto standard. Released on August 12, 1981, it was created by a team ...
,
IBM PCjr The IBM PCjr (pronounced "PC junior") was a home computer produced and marketed by IBM from March 1984 to May 1985, intended as a lower-cost variant of the IBM PC with hardware capabilities better suited for video games, in order to compete mor ...
,
Nascom The Nascom 1 and 2 were single-board computer kits issued in the United Kingdom in 1977 and 1979, respectively, based on the Zilog Z80 and including a keyboard and video interface, a serial port that could be used to store data on a tape cassette ...
,
MSX MSX is a standardized home computer architecture, announced by Microsoft and ASCII Corporation on June 16, 1983. It was initially conceived by Microsoft as a product for the Eastern sector, and jointly marketed by Kazuhiko Nishi, then vice-p ...
,
Amstrad CPC The Amstrad CPC (short for ''Colour Personal Computer'') is a series of 8-bit home computers produced by Amstrad between 1984 and 1990. It was designed to compete in the mid-1980s home computer market dominated by the Commodore 64 and the Si ...
, and
BBC Micro The British Broadcasting Corporation Microcomputer System, or BBC Micro, is a series of microcomputers and associated peripherals designed and built by Acorn Computers in the 1980s for the BBC Computer Literacy Project. Designed with an emphas ...
from
Acorn Computers Acorn Computers Ltd. was a British computer company established in Cambridge, England, in 1978. The company produced a number of computers which were especially popular in the United Kingdom, UK, including the Acorn Electron and the Acorn Archi ...
all contained a built-in
relay A relay Electromechanical relay schematic showing a control coil, four pairs of normally open and one pair of normally closed contacts An automotive-style miniature relay with the dust cover taken off A relay is an electrically operated switch ...
for controlling an external tape recorder. Toggling the motor control relay in a tight loop would reduce the relay's longevity.


Amiga

The floppy drive of the
Amiga 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 32-bit processors, 256 KB or more of RAM, mouse-based GUIs, and significantly improved graphi ...
personal computer could be made to produce noises of various pitches by making the drive heads move back and forth. A program existed which could play
El Cóndor Pasa EL, El or el may refer to: Religion * El (deity), a Semitic word for "God" People * EL (rapper) (born 1983), stage name of Elorm Adablah, a Ghanaian rapper and sound engineer * El DeBarge, music artist * El Franco Lee (1949–2016), American po ...
, more or less correctly, on the Amiga's floppy drive. As some sounds relied on the head assembly hitting the stop, this gradually sent the head out of alignment.


LG CD-ROM drives

Certain models of LG CD-ROM drives with specific firmware used an abnormal command for "update firmware": the "clear buffer" command usually used on CD-RW drives. Linux uses this command to tell the difference between CD-ROM and CD-RW drives. Most CD-ROM drives dependably return an error for the unsupported CD-RW command, but the faulty drives interpreted it as "update firmware", causing them to stop working (or, in casual parlance, to be " bricked").


MSi Laptops UEFI

Systemd systemd is a software suite that provides an array of system components for Linux operating systems. Its main aim is to unify service configuration and behavior across Linux distributions; Its primary component is a "system and service manager ...
mounts variables used by
Unified Extensible Firmware Interface UEFI (Unified Extensible Firmware Interface) is a set of specifications written by the UEFI Forum. They define the architecture of the platform firmware used for booting and its interface for interaction with the operating system. Examples of f ...
on
Linux Linux ( or ) is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged as a Linux distribution, which in ...
system's
sysfs sysfs is a pseudo file system provided by the Linux kernel that exports information about various kernel subsystems, hardware devices, and associated device drivers from the kernel's device model to user space through virtual files. In addition t ...
as writable by the root user of a system. As a result, it is possible for the
root user In computing, the superuser is a special user account used for system administration. Depending on the operating system (OS), the actual name of this account might be root, administrator, admin or supervisor. In some cases, the actual name of th ...
of a system to completely brick a system with a non-conforming UEFI implementation (specifically some MSi laptops) by using the rm command to delete the /sys/firmware/efi/efivars/ directory, or recursively delete the
root directory In a computer file system, and primarily used in the Unix and Unix-like operating systems, the root directory is the first or top-most directory in a hierarchy. It can be likened to the trunk of a tree, as the starting point where all branches ...
.


Game Boy

The
Game Boy The is an 8-bit fourth generation handheld game console developed and manufactured by Nintendo. It was first released in Japan on April 21, 1989, in North America later the same year, and in Europe in late 1990. It was designed by the same tea ...
's LCD screen can be turned off by game software. Doing so outside of the
vertical blanking interval In a raster scan display, the vertical blanking interval (VBI), also known as the vertical interval or VBLANK, is the time between the end of the final visible line of a frame or field and the beginning of the first visible line of the next fram ...
can allegedly damage the hardware.


Dragon 32

The
Dragon 32 The Dragon 32 and Dragon 64 are home computers that were built in the 1980s. The Dragons are very similar to the TRS-80 Color Computer, and were produced for the European market by Dragon Data, Ltd., initially in Swansea, Wales before mo ...
CPU clock speed was defined by a programmable clock divider which could be programmed by the user to increase the CPU speed by 50% or 100% and theoretically, 150% (though selecting this speed caused the system to crash.) The installed CPU, the 6809E was originally rated at 1Mhz with the Dragon 32 running at . A speed uplift to 1.33Mhz appeared mostly stable whereas an uplift to would cause video sync to be lost. It was publicised at the time that the increased heat produced by the speed increase would eventually damage the CPU. allowed for double speed with graphics still displayed properly. lost video sync.


See also

* HCF (Halt and Catch Fire) *
Pentium F00F bug The Pentium F00F bug is a design flaw in the majority of Intel Pentium, Pentium MMX, and Pentium OverDrive processors (all in the P5 microarchitecture). Discovered in 1997, it can result in the processor ceasing to function until the computer ...
*
Stuxnet Stuxnet is a malicious computer worm first uncovered in 2010 and thought to have been in development since at least 2005. Stuxnet targets supervisory control and data acquisition (SCADA) systems and is believed to be responsible for causing subs ...
, malware designed to cause physical wear in industrial centrifuges *
Bricking A brick (or bricked device) is a mobile device, game console, router or other consumer electronic device that is no longer functional due to corrupted firmware, a hardware problem, or other damage. The term analogizes the device to a brick's ...
, the act of misconfiguring a device so as to make it cease functioning * CIH (computer virus)


References

{{Reflist, refs= {{cite journal , title=Konrad Zuse's Legacy: The Architecture of the Z1 and Z3 , author-last=Rojas , author-first=Raúl , author-link=Raúl Rojas , journal=
IEEE Annals of the History of Computing The ''IEEE Annals of the History of Computing'' is a quarterly peer-reviewed academic journal published by the IEEE Computer Society. It covers the history of computing, computer science, and computer hardware. It was founded in 1979 by the AFIP ...
, volume=19 , number=2 , date=April–June 1997 , pages=5–16 –10, doi=10.1109/85.586067 , url=http://ed-thelen.org/comp-hist/Zuse_Z1_and_Z3.pdf , access-date=2022-07-03 , url-status=live , archive-url=https://web.archive.org/web/20220703082408/http://ed-thelen.org/comp-hist/Zuse_Z1_and_Z3.pdf , archive-date=2022-07-03 , quote-page=10 , quote=There are a lot of details that the engineer designing the "microprogram" must keep in mind, otherwise short circuits can destroy the hardware. The Z1 with its mechanical design was still more sensitive in this respect than the Z3. Even after it was completed, there were sequences of instructions that the programmer had to avoid in order not to damage the hardware. One of those sequences was inadvertently tried at the Berlin Museum of Technology and Transportation, which led to slight damaging of the reconstructed Z1 in 1994. (12 pages)


External links


Commodore PET killer poke discussion
Computer jargon Hardware bugs Denial-of-service attacks