An early example of this can be seen on the Atari VCS (2600) console. With the "Space Invaders" game, one could hold down reset when powering on the machine and get a two shot mode. As word of that got around, people would rapidly cycle the power, and or partially insert the power cord into the receptacle on the rear of the machine to get odd game effects and states.

Was this ever done to any useful effect on vintage / retro computers?

  • My memory isn't clear enough about this to post this as an answer, but I seem to recall seeing a writeup in the 1980s of a way to remove or partially remove a cartridge from an Atari 800 in such a way that the machine partially reset and continued to be usable so you could then look at or save the memory where the cartridge resided to disk. – LAK May 5 '20 at 13:32
  • Yes! Great recall. I do recall the same now that you mention it. – Spud May 6 '20 at 17:23

I think it would be unlikely to work on computers, as opposed to consoles.

The trick relies on corrupting values in RAM (by disrupting the DRAM refresh cycle) without also corrupting the game code; this worked in the arcade and on consoles, where the game code was held in ROM and could not be corrupted.

But on a home computer, games were normally loaded from disk or tape and held in RAM, and the values the game logic relied on would be initialised either simultaneously with or after the game had loaded. So any attempt to corrupt RAM would also corrupt the game code, preventing it from working at all.

It is possible that this trick inspired later game-cheating tools like the Action Replay, which could modify RAM deliberately and precisely. These were indeed released for some home computers as well as consoles.

  • this tehnique also can damage the machine, by continuous switch on/off. I don't think this was the inspiration for Action Replay carts. Every "embedded system" needs debugging tools. – Jean-François Fabre May 6 '20 at 6:51

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