RAM used to store samples for MIDI playback. Sound cards like the AWE32 had 512k standard which was expandable with standard SIMMs, the AWE64 Gold had 4mb onboard and was not expandable. The concept of sample RAM on consumer boards is now nonexistent as not too many people listen to MIDIs these days, though boards like the SB Live! implement Sample RAM using system RAM, which is a fairly good trade off. Dedicated samplers also contain sample RAM, but it's usually much more than any sound card would have, as it needs to hold a good deal of data at CD quality.