The POPCORN.DOC file that should be included with the game explains what you need to do, although it's in French if you don't have a translated copy.

Run the POPSPEED.EXE program with a parameter to set the game speed (e.g. "POPSPEED 1000"). The speed value is only set in memory, not recorded on disk, so you have to run POPSPEED once in each session before running the game. The speed value has always been something you have to experiment with to find your prefered speed, but of course the speed you get is also relative to DOSBox's cycles setting.

Note that POPSPEED passes the speed value to the game in an unusual way: in the offset of the INT 68h vector. Because of the initial vector DOSBox has for INT 68h, the default speed value used in the game is 4192 if you don't run POPSPEED.

Thanks for your advices

Unfortunately, using pop speed has exactly the same effect than playing with DOSbox's cycles to me: the non-game animation speed seems to be completely disconnected to the game speed.
Either I can play at the right speed, but have to wait several minutes for the main menu animation to play out, or I get normal menu animation, but the game in unplayable fast. 🙁

By the way, when the cycles are adjusted for the game, I can make the non-game animations behave correctly by using alt-F12 (unlock speed). It's like the game detects my actual PC speed at that time and adjusts to it (then getting slowed down by DOSbox's cycles settings), but the game section doesn't. Weird.

It's quite playable for me with cycles=300, popspeed 100. I'm not sure what to expect from the title/menu animation speed, but the pixel shower off the paddle and the horizontal scrolling message seem to be at proper speed. The game does check for vertical retrace, so there may be a slight speed difference depending on machine type (60 Hz for CGA, 70 Hz for VGA).

Thanks again.
I do get soemthing much better using your settings.

I find it strange though: popspeed has no effect whatsoever on the ball speed, only on the rest of the animations. the ball speed in only dependant on the cycles.