How does the GBA detect whether the cart is for GB/GBC or for GBA?
The cart connector inside of the GBA uses a switch to detect the cart type. If there are two small grooves on the back of the cart on the sides, then the GBA recognizes it as a GBA cart. These grooves are detected by a switch in the cart connector in the GBA. No grooves cause the switch to flip and 5 volts (gb/gbc carts) to be put on the cart instead of 3.3 volts (GBA carts). If you try to defeat this system you will maybe end up destroying a cart and maybe damage your GBA.
