I have an original Game Boy, and I know that saving is broken because Tetris won’t save my scores. How does saving work in Game Boy games, and are there any games that save without the use of the built-in save system?
Tetris didn't have any sort of save state for the high scores. According to this list, it appears that the high scores were effectively reset each time the Gameboy was powered off. It's not that there's some sort of save device in Tetris itself or the Gameboy that's broken, it's simply not designed to save the high scores.
The Gameboy itself has no usable internal storage for storing save data like the later systems do (with systems like the 3DS and Switch even including expandable storage via SD/MicroSD cards). The cartridges back then used a battery backup, which is to say that a portion of RAM was constantly powered by a small battery in the cartridge; as long as the cartridge was powered on periodically, the battery's life would be extended a bit. As these batteries would die, the ability to save after you turned the system off would disappear; you could keep your save data only as long as you could power the Gameboy continuously.
Since this was a problem, people eventually came up with a solution: external storage. There were devices made, like the Monster Brain, that sat between the cartridge and the system (a dongle), which would manage that memory and save to a more reliable medium, typically flash storage. In addition, these dongles sometimes allowed you to have multiple save games (e.g. multiple save games of Pokemon were possible), and your save would work even if you used a different cartridge than the original where you started the save.
You can fix a particular cartridge, but it requires disassembly of the cartridge and replacing the battery, which needed a security screw driver for the screws that Nintendo used, which you can get as part of a bundle from iFixIt and various hobby/specialist electronics stores. The batteries themselves are small button batteries, and pretty easy to replace, but buying a dongle can save the efforts of having to repair each cartridge individually.
NOTE: If you have any cartridges that still have batteries in them, you should have the batteries removed or replaced, since cells that old have a chance of leaking, and a leak can easily destroy the motherboard and may present a health hazard if the leak isn't contained in the cartridge. If attempting to perform a repair yourself, you should be extra careful whilst opening the cartridge in case there was a leak, and have a plan to safely dispose of those batteries.
Each cartridge that offers persistent saves are independent from all others. So, while your Tetris cartridge might not be able to save ever again, it wouldn't affect your Pokemon's cartridge ability to save. There's no single point of failure in the Gameboy that would prohibit any game from saving, as long as the cartridge and system were in working order, of course.
And yes, there are games that do not use battery backup as a save feature; instead, they were called passwords. Games of this sort would require you to write down various letters, numbers, or symbols to "save" your game, and to "load" your game, you would input the password. Games like Mega Man and Prince of Persia had no internal battery, and depended on the player writing down the code correctly and entering it correctly in order to continue playing later. There's a complete list of games that lists the basic characteristics of all Gameboy games, and there are a total of 157 that use passwords as a method for saving and loading game state.
Tetris won’t save my scores
Tetris is a ROM-ONLY cartridge, meaning it does not contain a RAM chip capable of saving progress. Game Boy does not offer a built in save either, so it's normal for Tetris not to save anything at all.
How does saving work in Game Boy games
When you insert a cartridge with RAM (like many MBC1 or 3 carts) it works like this:
- It gets mapped at 0xA000-0xBFFF memory region of Game Boy Memory Management Unit (MMU).
- It is accessed normally using memory writing instructions, like LD (0xA000),A.
- The Region 0xA000-0xBFFF is small (8Kb) so RAM mapping is available using special cart registers
- In order to retain the volatile memory, a power supply is required (hence the small battery)
are there any games that save without the use of the built-in save system
There is no "built-in" save system
are there any games that save without the use of the built-in save system?
I can't find a list of any gameboy games that don't use a battery for saves. As for the gameboy color there are a few games that have persistent save with no battery. I don't know what they are.
For completeness I'm going to list GameBoy Advance
Game Boy -- Ingame: Password (certain titles) On-Cart: SRAM (unknown type, likely CR1616)
Game Boy Color -- Ingame: Password (certain titles) On-Cart: SRAM (CR1616 or 2025 (the latter perhaps for titles with real-time clocks only?)), EEPROM (EEPROM is used by only a few titles)
Modem/Internet: Cell Phone Connector (Mobile Adapter GB) (Japan only) (Works with KDDI Cellphones and Pokemon Crystal JP version only – allows monster trading, a few other things)
Game Boy Advance -- Ingame: Password (certain titles) On-Cart: SRAM (CR2016) (32KB), EEPROM (0.5KB, 8KB), Flash RAM (64KB, 128KB), FRAM (32KB) (Type depends on game)
Tetris won’t save my scores.
It's already been answered that Tetris doesn't have any save abilities. Use save states with an emulator or take a picture with your phone to save your high score.