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===Commodore PET=== The [[Commodore PET|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 [[memory-mapped I/O|I/O]] register (<code>POKE 59458,62</code><ref name=":1">{{cite web|url=http://oldcomputers.net/pet2001.html|title=Commodore PET 2001 computer|publisher=oldcomputers.net|access-date=10 January 2011|archive-date=1 January 2011|archive-url=https://web.archive.org/web/20110101165618/http://oldcomputers.net/pet2001.html|url-status=live}}</ref>) 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.<ref name=":0" /> 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 [[cathode-ray tube|CRT]] monitor.<ref>{{cite web |url=http://www.6502.org/users/andre/petindex/poke/index.html |title=Killer Poke |work=PET index |first=André |last=Fachat |publisher=6502.org |access-date=10 November 2010 |archive-date=9 November 2010 |archive-url=https://web.archive.org/web/20101109023601/http://www.6502.org/users/andre/petindex/poke/index.html |url-status=live }}</ref> 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 [[Screen_burn-in|burn in]] to the display led to the nickname "killer poke";<ref name=":1" /> however, it is not known to have ever caused any permanent damage to the monitor.<ref>{{cite video |url=https://www.youtube.com/watch?v=7bMJ0NIuWU0 | archive-url=https://ghostarchive.org/varchive/youtube/20211211/7bMJ0NIuWU0| archive-date=2021-12-11 | url-status=live|title=The Killer POKE}}{{cbignore}}</ref>
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