MX23C6410PC-10 MX23C6410PC 64M-Bit (8M x 8/4M x 16) Mask ROM DIP42 X 2pcs | eBay
U-20 MASK ROM - Your One Stop Resource For The Roland U-20, U-220 And U-110 Synths - Patches, Tones, Utilities And Information. Also, tidbits of useful info for the D-70, Rhodes Model