--- In gbadev@y..., "Marco" <xinn@l...> wrote:
> But I've found a rom that use 2 different char base blocks
> (block 2 and 3)

You can fit 256 8-bit tiles or 512 4-bit tiles into a 16 KB bank.
If you have more than 256 tiles, just use tile numbers greater
than 255. If a tile number overflows e.g. tile bank 2, it will
spill into bank 3. (This has worked since the Super NES.)
Tetanus On Drugs for GBA uses this to display its wallpaper.

--
Damian