Be wary of "MAME 0.250 Full Set" downloads that are exactly 20GB. That is likely only the ROMs for games pre-1995. A true full set includes:
When looking for a 0.250 collection, you’ll encounter different formats: Full Non-Merged: mame 0250 rom set
: Available in several formats, including Split (where shared files stay in the parent zip), Merged (all files for a game in one zip), and Non-Merged (each zip is self-contained). Be wary of "MAME 0
This version featured a heavy emphasis on Konami, including support for regional variants on "Hornet" hardware and 3rd/4th player positions in titles like NBA Play By Play LCD Handhelds: mame 0250 rom set