on rom, You would have to verify data through each address. The easy way to do this is find someone with a rom chip reader, they can then do a verify to see if the chip is good, then can also dump any data to a file, then erase it and then reprogram it, if it reprograms, verifies and erases then it's most likely good. The ram chip can only be checked on a per address versus data method that I know of. If data or address is faulty then it will null or crash. All methods are mostly out of circuit. In circuit tests are difficult unless you know what your doing. Replace the ram and forget about it. Rom has specific data, thus more difficult since it contains software, this contact manufacture for another preprogramed chip. Good Luck
