MAME 0.84 was released in early 2004. This was the last version before the development team performed a massive "audit" that broke compatibility with a lot of older ROMs. Consequently, the 0.84 set became the de facto standard for:
Modern MAME requires huge "CHD" (Compressed Hunk of Data) files for games like Killer Instinct or NBA Jam . Version 0.84 predates heavy CHD usage. Almost every game in the set is a simple .zip file of ROM chips. Drop it in the folder, and it runs. mame 0.84 romset