>>12107086
>>12107120
Fast ROM is an expansion, "slow ROM" just means the stock SNES capabilities, which is 2.68 mhz speed. The fast ROM expansion uses special chips to overclock to 3.58 mhz, which is still half the speed of the Mega Drive. Other expansions that came out later, like the SA-1 or Super FX, did finally allow the system to be faster than a stock Mega Drive, but those were far more expensive cartridges.