1st is 1.8ghz 4500u 2nd one im not so sure 2.2 ghz and 3rd gen both goes about the same only different is 4th gen and 3rd gen and clock speed i wanna know that is 1st one good becoz its 4th gen or 2nd one good bcoz its has more clock speed and i would be happy if someone tell me the different between 3rd gen and 4th gen..