» Tue Jun 19, 2012 5:39 am
Unique weapons most likely don't fit into the categories of the perks in the smithing tree.
Basically, these perks don't actually "allow" you to upgrade them further, they simply boost your skill by a bit when you're upgrading that specific material.
So technically, when you're upgrading, say, the Dawnbreaker, it's ONLY your skill that's used.
When you're upgrading a Skyforge Steel Sword, you have your skill working, PLUS a hidden enchantment that says "smithing is X% better", but ONLY for that material (or the ones that you chose the according perks for)
EDIT: I tried having smithing at 100 without a single perk, and the the steel sword can be upgraded to the same "level" (the word besides the name of the weapon) as the Dawnbreaker