>>3775517That reminds me, Commodore machines had a ROM with useful code that games could use. A jump table was provided to reliably get to the code you wanted. The official developers manuals warned not to jump directly into the ROM, but always use the jump table.
Commodore updated its ROMs and the jump table was updated too, but only games made by Commodore would still work.
Game makers from other companies had ignored the tech manuals and jumped directly into the ROM. They had no reason to care. At that time all the profit came from the first six months a game was for sale.