For Morrowind that is correct but for Oblivion it was not 'all-encompassing' actually :

"alters the magnitude of any spell effect (from a spell being cast, or from an enchantment on a weapon or staff). Certain types of poison effects are also altered: Damage fatigue, Damage health, Damage attributes, Damage magicka, Silence, Drain attributes, Drain magicka, Drain health, Drain fatigue, and Burden poisons ARE resisted by resist magic. Paralysis and Elemental damage (Fire, Frost, and Shock damage) poisons ARE NOT resisted by resist magic. In other words, all spells are resisted by Resist Magic and all poisons except for Paralysis and Fire/Frost/Shock Damage are resisted by Resist Magic, but since NPCs don't use Fire/Frost/Shock poisons players don't have to worry about them."

http://www.uesp.net/wiki/Oblivion:Magical_Effects#Resistances_and_Weaknesses

Ah, I never realised it was different in Oblivion.
Thanks guys

The key word in their is poisons...

"Elemental damage (Fire, Frost, Shock damage) poisons are not resisted by resist magic..."

But... "all spells are resisted by Resist Magic and all poisons except for Paralysis and 'elemental damage'"

I see, never noticed that since the NPCs never used them. The line between poisons and actual magic is sort of confusing though.

Yeah it looks conusing, now I'm not even sure about it. I will have to do more research on the subject ( long time since I played oblivion )

EDIT:
I have just read more about the subject.
You were right Indalus, my bad
In Oblivion magic resistance was all-encompassing apparently.

How about this..

5% resist magic enchant. Seems harmless right??
Enchanting perk enchanter (100%) bonus to enchants = 10%
Enchanting perk extra effect (double encnahnt) = 20%
4 pieces of armor = 80%

And you still have 3 pieces left: necklace and two rings..
Not to mention Breton (25%) and magic resistance (alteration) 30%

The more i think about it, I think "extra effect" is going to be only 1 enchant..
Like you have 7 pieces of equipment, but it will allow only 1 piece to carry double enchant..

I would bet you cannot have the same two enchantments on one piece of armour, just like in the last games.

I have no doubt that if there is not a cap, 100% resistance/reflect/absorb etc will be doable. Of course, it is up to you if you would use this. I would prefer there to be a cap, but if not will try to aim for 100% unkillable eventually

The extra effect is weapons only

Are you sure?
Extra Effect : "Can put two enchantments on the same item"
I remember the other description but it was from old leaked material ( 2 months old )

The perk says item not weapon. In the pickpocket tree there are separate perks for pickpocking equpped weapons and equipped items, so it probably would have said weapon in the perk description if it was only weapons.

No I'm not sure. Wiki had the old version when I posted that comment. Seems to have changed though.

I am curious to see how some of this pans out not just for resist but for all stackable things.

Are they additive?
If so is there a limit?
Does the limit vary by effect?

Getting rid of the additive part would solve pretty much every enchanting "abuse" people complained about, but it would be less fun and if not explicit highly annoying for people who are unaware of it.

Spell resistance and resist magic are two DIFFERENT spell effects and do not build on each other.

For instance you get hit by a spell that normally does 100 damage

You have 50% magic absorption and 50% magic resist...

So the result means you resist 50% of the spell, so it does only 50 damage to you and then you absorb 50% of the spell which means you absorb 25 magica, but you still get hurt by 25. (Whether absorbion or resist is calculated first I don't know, you may swap them around, but you'll get the same ending damage to your character)

So Spell Absorption now works all the time but the amount of the spell which you absorb is determined by the magnitude of it?

In Oblivion, absorbing a spell means it will be absorbed entirely, but the magnitude of the spell determined the chance by which Spell Absorption would occur.

edited to remove rudeness. I don't like people stepping on my Breton's toes.

Yes, this will break the game, no spells/poisons/enchants/anything besides a physical strike can hurt a 100% resist breton. I did the same thing in oblivion/shivering isles.

There are many many ways to break this game. Chameleon jumps to mind. Morrowinds infinite magic or - any loop on a skill increase.
Or the difficulty slider, that can also make you unkillable unless you try to be killed.

It is a single player game.

I don't understand why people seem to think that it will be easy to acquire these perks. Atronach for example is at the end of the skill tree and requires lv 100 alteration. Magic resistance is 3 separate perks and we only know the stats of the first one, lv 30 for 10 points. For all we know (unless there has been new info) part 2 of this could be lv 35 for 15, lv 50 for 20 points...

(unrelated) I just realized when writing 'Atronach' in this post, that I have been mispronouncing it since TES 3! I've always said it Ann-toh-rock

Actually in oblivion 100% magic resistance made you immune to all hostel magic, elemental or otherwise. I had a Brenton with the mundane ring that I got at level 36. It gave me a 50% magic resist. Add that to the natural 50% of the brenton made you god like. On top of that I had a ring that made you immune to poison,disease, and parallelization. And thats not modded, as im on xbox. I can get on there and get the names of the items but i really dont want to. Add reflect damage enchantments from the sigil stones and you were immune to everything