Many Yamaha items, like the RS7000 and the Motif6 (...7 & 8) are expandable with RAM - specifically SIMM32Q. BUT, the Yamaha stuff is really picky, and needs the Simms to be an exact match. Otherwise, units with more than one Simm will one see ONE Simm.
There's always a little white sticker on the chip itself that has a lot number (eg: CT7223, or HK9201). We need to make sure that if two Simm's are going into a Yamaha unit, that they are an "EXACT MATCH".