The original form of the tournament, before jousting, was the
mêlée, which was pretty much a mock war, and went on for hours, and much like a Mount&Blade battle in the way that the fighting could disperse over quite a large area with participants using terrain to their advantage, pursuing each other, ambushing in forested areas, and even resting to treat injuries before returning to the fight.
Tankai said:
One thing that mainly bugs me is the death ration in these events. I mean, there are references to blunt weapons in later ages, but how were things in the 12th century for example? Taking prisioners is all fine, but you can't do it properly as long as you have other opponents in the field. So, did they die a lot or what?
In a mêlée normal weapons were used, and death was not an unusual occurence despite the aim to capture the opponent, though I would not say it happened a lot. I'm guessing it was more likely to happen at the beginning of the mêlée where teams would couch lances and charge at each other, colliding en masse in the middle. The fact that certain tournaments were remembered by the notable knight or knights who died during it suggests actual fatalities were low, but injuries would be common.
With the prisoners, knights would know who the best prize was on the field from the team colours and equipment of the participants, and would often gang up on them. Inexperienced knights were also found out and taken out of the fight quickly. In a free-for-all having other opponents preventing you from taking prisoners isn't much of a consideration, but with teams tactics would have been devised in order to take prisoners most effectively. William Marshal, for instance, had the nifty trick of riding alongside his enemy and taking hold of their reins and leading the knight away from the battle where he could be more easily captured. Also, there weren't many rules either, and there are records of teams not charging into the battle until several hours had already passed and the other teams were exhausted.
I think the introduction of blunted weapons and the general sanitisation of the tournament came in the early 14th century.
But I do know that they were established at least as far back as the writings of Geoffroi de Charny, since he mentions them in his Book of Chivalry, which he wrote around the 1340's. In fact he makes a distinction between the tournament and the joust, in that the jousting is the lowest rung in the ladder as far as what deserves honorable praise for deeds of arms, with tournaments coming in just above that. 
