Green Knight--
Basic task resolution couldn't be simpler--roll less than or equal to your skill or the difficulty, and you succeed.
For combat, a couple additional levels of success are added--you and your foe each roll a d20 and compare the results to your respective skills.
If a skill is greater than 20, it is considered to be equal to 20, and the excess is added to the d20 roll--20 is the maximum that can be scored (for example, a knight with a sword skill of 25 would roll d20+5, and a die roll of 15-20 would be considered a 20).
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Critical Success: A roll equal to your skill (so the knight in the example above would critical on a roll of 15-20).
Tie: Your successful roll equals your foe's successful roll; SWORD BREAKS NON-SWORD; NO DAMAGE.
Success: A roll less than your skill (normally automatic for the knight in the above example), AND greater than foe's successful roll.
Partial Success: A roll less than your skill, BUT less than your foe's successful roll.
Failure: A roll greater than your skill (not possible for the knight in the above example, unless circumstances reduce his skill).
Fumble: DROP WEAPON on a roll of natural 20, IF your adjusted skill is not 20 or greater (so the knight above could not normally fumble).
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COMBAT RESULTS
Crit vs Crit: No damage; Sword breaks non-sword.
Crit vs Fail/Fumble: Double damage to foe; Foe's shield ignored.
Crit vs Success/Partial: Double damage to foe; Foe's shield added to armour.
Success vs Fail/Fumble: Normal damage to foe; Foe's shield ignored.
Success vs Partial: Normal damage to foe; Foe's shield added to armour.
Partial vs Success: Suffer normal damage; add shield to armour.
Fail/Fumble vs Success: Suffer normal damage; may not add shield to armour.
Partial vs Crit: Suffer double damage; add shield to armour.
Fail/Fumble vs Crit: Suffer double damage; may not add shield to armour.
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MISC...
--Damage is based on STR/SIZ, and consists of multiple d6 (3-4d6 for an average man with a sword; knights typically average one die more).
--Armour reduces damage (a mail hauberk absorbs 10pts per blow).
--A typical knight's shield grants an additional 6pts of armour protection when successfuly deployed.
--HPs equal SIZ+CON
--Knockdown: If damage (before reduction for armour) is equal to or greater than SIZ, roll vs DEX or fall down.
--Auto-Knockdown: If damage (before reduction for armour) is double or more your SIZ, you are automatically knocked down.
--Unconscious at HP/4
--Major Wound: Damage (after reduction for armour) greater than or equal to your CON.
--When fighting multiple foes, you may split your weapon skill amongst them in any manner you see fit. If no weapon skill is applied versus a given foe, he may make an un-opposed skill roll (i.e. any roll less than or equal to his skill succeeds, and you may not add your shield to your armour).
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Well, that's it in a nutshell. Of course, there are many other options that modify this--feinting, defending, evading, dodging, relative height, etc...
Hope this serves to whet your appetite