Can someone give me a basic explanation of why some games work and some dont? Is there an easy way to make em all work?
To answer in reverse:
No, not all games in official mame. (see below)
My basic is pretty long:
Case 1: Original machine saved all high scores when it was turned off.
If mame properly emulates the game, mame will save the high scores, too.
Case 2: Original machine saved some high scores when it was turned off.
If mame properly emulates the game, mame by default will save the same high scores and not save the same high scores as the original game (example: one game might same just the top 3 of the top 10 list).
Case 3: Original machine did not save high scores when it was turned off.
Mame by default will not save the high score, also.
Summary of three cases: Mame by default will emulate the original game's save high score, and exiting the game is like turning off the machine.
Now, if you want to save the high score even though the original machine didn't (cases 2 & 3), there are three ways to do so:
Method 1: use auto save state
Emulates like you left the machine on when you exit the game, and starts off where you last exited when you start up the game again. (Sometimes manual save state works even when auto statestate doesn't.)
Problems: not all games support auto save state, a saved game probably won't work in a different version of mame if any part of the emulation was changed (such the cpu, sound, video, or game driver). (If used manual save state because auto doesn't work, might cause crashes or wierd behivior, and even higher chance won't work on newer/older version of mame.)
Method 2: use the hiscore.dat file official mame removed
The file is a list of games and the memory locations that holds the high scores, and the contents of that memory location (IOW, the high scores) are saved on exit are dropped back in at restartup.
Problems: need to CYO or use a devivative of mame, can cause crashes or other wierd behivior (the reason it was dropped from official mame), if a game is not on the list it won't be saved, sometimes a score doesn't work on newer mame (
much rarer that savestate though).
Method 3: use some other way
Including screen snaps, photographs, video, writing on dry erase board. Works on all games.
Problems: "not the same"