Gameboy Development Forum

drev · 2025-04-19 15:57:03

I'm writing a GBDK Mario Land. (https://github.com/odrevet/marioland-gbdk)

Level data is generated from PNG files. the level arrays are quite large—about 4800 unsigned char per level.

However, levels 3-1, 4-1, 4-2, and 4-3 are larger. For example, level 3-1 is an array of 7040 unsigned char.

When a ROM is compiled with any of these "large levels," the game crashes. I don't understand why, as I am using a 8 banks cartridge,

ROM usage without level 3-1:

Bank Range Size Used Used% Free Free%
----- ---------------- ------- ------ ----- ------ -----
ROM_0 0x0000 -> 0x3FFF 16384 15597 95% 787 5%
ROM_1 0x4000 -> 0x7FFF 16384 16289 99% 95 1%
ROM_2 0x4000 -> 0x7FFF 16384 16215 99% 169 1%
ROM_3 0x4000 -> 0x7FFF 16384 15863 97% 521 3%
ROM_4 0x4000 -> 0x7FFF 16384 1559 10% 14825 90%

ROM usage with level 3-1:

Bank Range Size Used Used% Free Free%
----- ---------------- ------- ------ ----- ------ -----
ROM_0 0x0000 -> 0x3FFF 16384 15597 95% 787 5%
ROM_1 0x4000 -> 0x7FFF 16384 16375 100% 9 0%
ROM_2 0x4000 -> 0x7FFF 16384 16344 100% 40 0%
ROM_3 0x4000 -> 0x7FFF 16384 15959 97% 425 3%
ROM_4 0x4000 -> 0x7FFF 16384 8320 51% 8064 49%

their is still some free space when the level is added

Given that each bank is 16KB, shouldn’t the max size of a level array be 16,384 bytes?

So what is the actual maximum supported size for an arrayin ROM ?

The obvious fix is to split levels into multiple sub-level chunks or to compress the data. But out of curiosity, why does the game crash when a level is large? Is it really because of the level size that the game crashes ?

toxa · 2025-04-20 14:52:43

the maximum array size in GBDK-2020 equals to 0xffff. but that does not mean you can DEFINE such constant array, because that is a whole SM83 address space. in practice, your constant arrays must fit 16384, or else you get errors while linking. speaking about your project, arrays look smaller than 16384, which is fine. it is unlikely, that arrays themselves are the source of your problem, more likely, some OTHER problem (likely with the bank switching) triggers when stuff is automatically tossed to the different banks. probably some of your code assumes that some asset is located in the same bank with the other asset, but they are not anymore, after adding levels.

the other problem with your code is enormous amount of warnings, fix them all. it is a good habit to fix warnings as if they were errors.

another suggestion is to use gbdk/* includes, rather than gb/* includes.

drev · 2025-04-20 16:47:30

One again thanks for your response, the error was indeed having at some point the player related functions on autobank and then forgot about that
the crash ocurred because large levels were moving thinks around
At this point the levels are all loaded and I will fix warings and includes
BR

bbbbbr · 2025-04-23 05:20:32

Cool project! Looking forward to hearing more about it as it progresses.

Gameboy Development Forum

Ads

#1 2025-04-19 15:57:03

Maximum size of an array in rom

#2 2025-04-20 14:52:43

Re: Maximum size of an array in rom

#3 2025-04-20 16:47:30

Re: Maximum size of an array in rom

#4 2025-04-23 05:20:32

Re: Maximum size of an array in rom

Board footer