Killer poke
Encyclopedia
In computer jargon, a killer poke is a method of inducing physical hardware
damage on a machine and/or its peripheral
s by the insertion of invalid values, via e.g. BASICs POKE
command, into a memory-mapped
control register
. The term is typically used to describe a family of fairly well known tricks that can overload the analog electronics in the CRT
monitor
s of computers lacking hardware sanity checking (notable examples being the IBM Portable
and Commodore PET
; a similar trick is reported having been done to Atari ST
displays).
-specific killer poke is connected to the architecture of that machine's video rasterizer circuits. In early model 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 on the screen much faster. When the PET range was revamped with updated hardware, it was quickly discovered that performing the old trick on the new hardware led to disastrous behavior by the new video chip, causing it to destroy the PET's integrated CRT
monitor.
Model III 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, and was 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
that could permanently damage the hardware.
, IBM PCjr
, MSX
, and BBC Micro
from Acorn Computers
all contained a built-in relay for controlling an external tape recorder. Toggling the motor control relay in a tight loop would reduce the relay's longevity.
, 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.
's LCD screen can be turned off by game software. Doing so outside of the vertical blanking interval
can damage the hardware.
Computer hardware
Personal computer hardware are component devices which are typically installed into or peripheral to a computer case to create a personal computer upon which system software is installed including a firmware interface such as a BIOS and an operating system which supports application software that...
damage on a machine and/or its peripheral
Peripheral
A peripheral is a device attached to a host computer, but not part of it, and is more or less dependent on the host. It expands the host's capabilities, but does not form part of the core computer architecture....
s by the insertion of invalid values, via e.g. BASICs POKE
PEEK and POKE
In computing, PEEK is a BASIC programming language extension used for reading the contents of a memory cell at a specified address. The corresponding command to set the contents of a memory cell is POKE.-Statement syntax:...
command, into a memory-mapped
Memory-mapped I/O
Memory-mapped I/O and port I/O are two complementary methods of performing input/output between the CPU and peripheral devices in a computer...
control register
Hardware register
In digital electronics, especially computing, a hardware register stores bits of information, in a way that all the bits can be written to or read out simultaneously.The hardware registers inside a central processing unit are called processor registers....
. The term is typically used to describe a family of fairly well known tricks that can overload the analog electronics in the CRT
Cathode ray tube
The cathode ray tube is a vacuum tube containing an electron gun and a fluorescent screen used to view images. It has a means to accelerate and deflect the electron beam onto the fluorescent screen to create the images. The image may represent electrical waveforms , pictures , radar targets and...
monitor
Computer display
A monitor or display is an electronic visual display for computers. The monitor comprises the display device, circuitry, and an enclosure...
s of computers lacking hardware sanity checking (notable examples being the IBM Portable
IBM 5100
The IBM 5100 Portable Computer was a portable computer introduced in September 1975, six years before the IBM PC. It was the evolution of a prototype called the SCAMP that was developed at the IBM Palo Alto Scientific Center in 1973. In January 1978 IBM announced the IBM 5110, its larger cousin,...
and Commodore PET
Commodore PET
The Commodore PET was a home/personal computer produced from 1977 by Commodore International...
; a similar trick is reported having been done to Atari ST
Atari ST
The Atari ST is a home/personal computer that was released by Atari Corporation in 1985 and commercially available from that summer into the early 1990s. The "ST" officially stands for "Sixteen/Thirty-two", which referred to the Motorola 68000's 16-bit external bus and 32-bit internals...
displays).
The Commodore PET
The PETCommodore PET
The Commodore PET was a home/personal computer produced from 1977 by Commodore International...
-specific killer poke is connected to the architecture of that machine's video rasterizer circuits. In early model PETs, writing a certain value to the memory address of a certain I/O
Memory-mapped I/O
Memory-mapped I/O and port I/O are two complementary methods of performing input/output between the CPU and peripheral devices in a computer...
register ( POKE 59458,62 ) made the machine able to display text on the screen much faster. When the PET range was revamped with updated hardware, it was quickly discovered that performing the old trick on the new hardware led to disastrous behavior by the new video chip, causing it to destroy the PET's integrated CRT
Cathode ray tube
The cathode ray tube is a vacuum tube containing an electron gun and a fluorescent screen used to view images. It has a means to accelerate and deflect the electron beam onto the fluorescent screen to create the images. The image may represent electrical waveforms , pictures , radar targets and...
monitor.
TRS-80 Model III
The TRS-80TRS-80
TRS-80 was Tandy Corporation's desktop microcomputer model line, sold through Tandy's Radio Shack stores in the late 1970s and early 1980s. The first units, ordered unseen, were delivered in November 1977, and rolled out to the stores the third week of December. The line won popularity with...
Model III 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, and was 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 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 error must be considered.-Component failure:A part...
that could permanently damage the hardware.
Cassette Tape Relay
The TRS-80 Color ComputerTRS-80 Color Computer
The Radio Shack TRS-80 Color Computer was a home computer launched in 1980. It was one of the earliest of the first generation of computers marketed for home use in English-speaking markets...
, IBM PCjr
IBM PCjr
The IBM PCjr was IBM's first attempt to enter the home computer market. The PCjr, IBM model number 4860, retained the IBM PC's 8088 CPU and BIOS interface for compatibility, but various design and implementation decisions led the PCjr to be a commercial failure.- Features :Announced November 1,...
, MSX
MSX
MSX was the name of a standardized home computer architecture in the 1980s conceived by Kazuhiko Nishi, then Vice-president at Microsoft Japan and Director at ASCII Corporation...
, and BBC Micro
BBC Micro
The BBC Microcomputer System, or BBC Micro, was a series of microcomputers and associated peripherals designed and built by Acorn Computers for the BBC Computer Literacy Project, operated by the British Broadcasting Corporation...
from Acorn Computers
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 UK. These included the Acorn Electron, the BBC Micro, and the Acorn Archimedes...
all contained a built-in relay for controlling an external tape recorder. Toggling the motor control relay in a tight loop would reduce the relay's longevity.
Commodore Amiga
The floppy drive of the Commodore Amiga 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 PasaEl Cóndor Pasa (song)
El Cóndor Pasa is a song from the zarzuela El Cóndor Pasa by the Peruvian composer Daniel Alomía Robles, written in 1913 and based on traditional Andean folk tunes....
, 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 be bricked.Game Boy
The Game BoyGame Boy
The , is an 8-bit handheld video game device developed and manufactured by Nintendo. It was released in Japan on , in North America in , and in Europe on...
's LCD screen can be turned off by game software. Doing so outside of the vertical blanking interval
Vertical blanking interval
The vertical blanking interval , also known as the vertical interval or VBLANK, is the time difference between the last line of one frame or field of a raster display, and the beginning of the first line of the next frame. It is present in analog television, VGA, DVI and other signals. During the...
can damage the hardware.
See also
- HCF (Halt and Catch Fire)Halt and Catch FireHalt and Catch Fire, known by the mnemonic HCF, refers to several computer machine code instructions that cause the CPU to cease meaningful operation...
- Pentium F00F bug
- Scratch MonkeyScratch monkeyA Scratch Monkey is a term used in hacker jargon, as in "Before testing or reconfiguring, always mount a scratch monkey", a proverb used to advise caution when dealing with irreplaceable data or devices...