區(qū)別一：

As far as I know, he's going to Chicago.（用在更加正式的場合）

So far as I know, he's going to Chicago.（用在一般的/順便一些的場合）

區(qū)別二：

as far as used when you are asking or talking about the distance between two places or the distance that has been travelled or is to be travelled：（表示“距離”時，as far as在肯定、否定句中都可用，但so far as只能夠用在否定句中）

We'll go by train as far as London, and then take a bus.

We didn't go as far as the others.（可用so far as）

區(qū)別三：

as far as used when you are asking or talking about the degree to which something is true or possible（表示“程度”意義時，只能用as far as）：

His parents supported him as far as they could.

Plan your route in advance, using main roads as far as possible.