Killer poke

The PET-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[2]) made the machine able to display text on the screen much faster. When the PET range was revamped with updated hardware, it was discovered that 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.[3] However this is not known to have ever caused any permanent damage to the monitor.[4]

The Commodore 64 had an optional external 5-1/4" floppy drive. The Commodore 1541 contained a 6502 microprocessor which was used to run Commodore DOS and also to manage the drive mechanism. The drives stored data on 40 tracks (#0–39), 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 techniques that used non-standard disk formats with unusual track counts. The Commodore 1571 had an optical head stop instead of a mechanical one.

The TRS-80 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, accomplished by writing to a specific memory-mapped control register.[5] 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.

The TRS-80 Color Computer, IBM PC, IBM PCjr, Nascom, MSX, Amstrad CPC, and BBC Micro from Acorn Computers all contained a built-in relay for controlling an external tape recorder.[6] Toggling the motor control relay in a tight loop would reduce the relay's longevity.

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 Pasa, more or less correctly, on the Amiga's floppy drive.[7] As some sounds relied on the head assembly hitting the stop, this gradually sent the head out of alignment.

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").[8]

Systemd mounts variables used by Unified Extensible Firmware Interface on Linux system's sysfs as writable by the root user of a system. As a result, it is possible for the root user 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.[9]

The Game Boy's LCD screen can be turned off by game software. Doing so outside of the vertical blanking interval can allegedly damage the hardware.[10]

The Dragon 32 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 0.89Mhz. A speed uplift to 1.33Mhz appeared mostly stable whereas an uplift to 1.78Mhz 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. POKE 65495, 0 allowed for double speed with graphics still displayed properly. POKE 65497, 0 lost video sync.