MySQL323

Greetings,

So I was wondering what is really behind the older version of MySQL's hashing algorithm - MySQL 4.1.0? As of MySQL 4.1.1 it's clear that it is sha1(unhex(sha1($pass))) producing a 41-byte string but what about the one that produces a 16-byte string?

Also, why does it have multiple possible plaintext values?

Hope this hasn't been discussed before since I didn't bother to check.