Also, regarding ROM states... please see this section in our wiki for details on what they mean. "Mostly correct" is the combined state for sets that are known to contain "bad dumps" and/or to be "missing dumps" (aka as "best available"). So it's no wonder that most games work even in this state; that's expected.

If unsure, I suggest using the ROMAlyzer to see what's "wrong" with a set. Dumps that are known-to-be-missing or known-to-be-bad are indicated with an "under construction" sign smile.

A mind is like a parachute. It doesn't work unless it's open. [Frank Zappa]