The game was originally designed for the PlayStation Portable's restricted 222 megahertz (MHz) processor. Ready At Dawn repeatedly contacted Sony regarding increasing the clock speed of the PSP on account of the difference to the game, and had developed a version of the game with higher speed. Sony released a firmware upgrade that allowed games to use the full 333 MHz processor. The faster processor allowed for more realistic blood effects, lighting effects, and shadows as well as improved enemy intelligence. The upgrade, however, noticeably decreases battery life.