Adderall is 75% dextroamphetamine and 25% levoamphetamine. It's the 25% levo that is shit and gives the CN side effects. Our great pharmaceutical companies came up with that combo after Dexadrine's patent ran out.
OK, but Modafinil or Armodafinil are comparatively safe to use long-term. By helping a person stay awake and not get tired, in this way it helps them to stay focused and concentrate longer, without the stimulant aspects of the other drugs.
It also doesn't cause a 'crash' as a small dosage works gradually and lasts long till it tapers off.