Most GB/GBC battery backed up games are equipped with three ram memory sizes, 8, 32, or 128 kilobytes.
On GameBoy DMG & GBC cartridges RAM memory chips are used to store user information and game advances or profiles, to save this information when power is off it uses a battery mounted inside the cartridge.
For 8 Kbyte Ram: it's a 28 pin chip, usually labeled as “64K RAM” or "64K WRAM it may be confusing because it’s noted in Kilobits. Read the label on top of the chip, it must have a 4 digit code. Ignore other characters, they only indicates manufacturer and date codes. The following are Known chips used by Nintendo.
For 32kByte Ram: It's a 28 pin SMD chip, in some boards it’s labeled as “256K RAM”, again it’s noted in Kilobits. Read the label on top of the chip, it must have a 5 digit code ending with 256. Ignore the rest of the characters, they only indicates manufacturer and date codes. Specific procedure for this type of memory will be explained later.
For other configurations: They are unsupported at this time.
Notes: *** NVRAM upgrade kits are not fully tested or developed for a NES/FC cartridge, in theory they shoiuld work, but because it is still a “work in progress" it may not work properly or may not work at all in this platforms.
Once you know the type and size of memory, you can purchase the right upgrade kit here.
For installation instructions click here.