Re-reading my old video game magazines from the mid-1990s, there's constant mentions of "USA import" games which were not released here and which "require an adapter". Many of the ads sold various devices which you put into the SNES cartridge slot and then put a USA game on top of, and then it would (allegedly) play on a PAL SNES, even though the game was made for American (NTSC) SNESes.
I get that it defeated any anti-piracy and region locking code. That much is not hard to understand.
But, since (if what I have understood is accurate) the PAL and NTSC machines were fundamentally different in the hardware in some important ways, how was it possible for a cheap little hardware thing to do this "conversion" which normally required the original programming team to spend significant resources to re-code and re-time the game speed/logic/physics/music to run on PAL after originally being made for Japan/USA (NTSC)?
They never once mentioned anything about the games not running "quite right", such as with sped-up (or slowed down) logic/music, bugs/glitches, etc. Not in the ads and not in the actual texts/answers by the editorial team of the magazines. This leads me to believe that this was simply possible and that I've been mistaken about the hardware being that different between PAL/NTSC.
Since they sold those adapters for not much money, they can't reasonably contain the missing/different hardware found only in NTSC SNES/SFC consoles... but maybe that's exactly how it was done?
Today, there are "EverDrives" and similar devices which also appear to allow you to play NTSC games on PAL hardware, but while I'm still curious about those, my question is primarily about the old ones which could actually be bought in 1994-1995, for example to play RPGs that were never released in Europe.