The chip in your PSP was designed to run faster than it does out of the box. By default, the CPU runs at 222Mhz, but the MIPS R4000 processor was designed to run at 333Mhz with a 166Mhz bus. I don't need to spell out for you what it means that the most powerful handheld gaming device is factory underclocked.
Well, Sony allowed developers to change the clock speed from within the game, starting with Bios 3.5, which GoW takes advantage of. What about the other games that turn into slideshows? How do you unlock the CPU and get them to run faster?