The framerate of the GB and GBA is 262144/4389 frames per second (roughly 59.7275), give or take clock inaccuracy.

The framerate of the DS and 3DS is 16756991/280095 frames per second (roughly 59.8261), give or take clock inaccuracy.

I'm mostly posting this for future reference since I have to look up the numbers too frequently.

@endrift Wait, so, when the DS and 3DS are in GBA backwards-compatibility mode, do they downclock slightly or are the games just a tad too fast?
@Jhynjhiruu I'm not sure but I think they run slightly too fast
@Jhynjhiruu That's roughly 0.165% too fast though so it would really only matter for speedruns
@endrift And I suppose it'd be pretty easy to correct the times automatically even then
@Jhynjhiruu hopefully the different games and saves don't affect this but I'll let you know in an hour if the copy of Ruby is a few seconds behind
@hazelnot @Jhynjhiruu I was informed that they do not have the same number of frames per intro loop so I aborted the test early