How could/can there exist NTSC->PAL converters for SNES and other classic game consoles?

Question

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.

Answer 1

These adapters do nothing else than defeat the lockout chip so that e.g. a PAL region console can be forcibly made to execute code from a cartridge whose content is originally intended to run on an NTSC region console.

Which simply means that if the software is made to expect certain features of the NTSC hardware (such as CPU clock speed, frame rate, etc) which are different when it is run on PAL hardware then it may not work so well.

Answer 2

The hardware is different, but not so different as to prevent most games from playing.

Yes, they ran slower because of the frame rate difference. That was par for the course, and quite a few commercially released PAL games had the exact same issue.

Yes, the music would be slower and off-pitch... this one was more likely to be corrected in the "official" releases (because it's easier than adjusting gameplay speed), but there were plenty that didn't (Castlevania for instance).

Yes, the display was a bit squished due to the difference in number of lines between the two TV standards — you could adjust your TV to make up most of the difference if you wanted.

But most games were playable and the differences were just a fact of life when living in PAL-land — if people even knew there were differences; a lot of people never would have had the chance to see the games in action on an NTSC system, so what would they compare to?

Only a relatively few games were unplayable or had graphical glitches — after all, the CPU and all of the peripherals were the same, and it was just timings that were different. Only code that relied on a specific number of CPU cycles between frames, or between the vertical blank and a particular line of the screen, would be liable to break. There was some of that in the NES collection, but most games were pretty well behaved.