AD&D Combat Round = 1 minute
Pretty long, eh? So let's check out AD&D 1st Edition DMG which holds forth extensively on the rationale for the combat round:
Combat is divided into 1 minute period melee rounds, or simply rounds, in order to have reasonably manageable combat. "Manageable" applies both to the actions of the combatants and to the actual refereeing of such melees. It would be no great task to devise an elaborate set of rules for highly complex individual combats with rounds of but a few seconds length. It is not in the best interests of an adventure game, however, to delve too deeply into cut and thrust, parry and riposte.But that's not all! It further goes on to say:
During a one minute melee round many attacks are made, but some are mere feints, while some are blocked or parried. One, or possibly several, have the chance to actually score damage. For such chances, the dice are rolled, and if the"to hit" number is equaled or exceeded, the attack was successful, but otherwise it too was avoided, blocked, parried, or whatever.And goes on even more to say:
Because of the relatively long period of time represented by the round, dexterity (dexterity, agility, speed, quickness) is represented by a more favorable armor class rating rather than as a factor in which opponent strikes the first blow.I understand how that combat round is an abstraction, but I'm certainly not in the one-minute combat round camp. Too long, and I find the exchanges and finer points of exchanges interesting (to a degree). And it doesn't make sense given the rate of fire rules in the PHB! Two minutes to fire one heavy crossbow bolt? One minute to fire an arrow from a composite bow? I understand the feint and exchange argument, but in the case of missile weapons you actually mark off ammo.
Fortunately, the PHB actually lays down the law very clearly early on without this very strange (dare I say defensive and unnecessary discussion on the combat round) by saying
In adventuring below ground, a turn in the dungeon lasts 10 minutes (see also MOVEMENT). In combat, the turn is further divided into 10 melee rounds, or simply rounds. Rounds are subdivided into 10 segments, for purposes of determining initiative (q.v.) and order of attacks. Thus a turn is 10 minutes, a round 1 minute, and a segment 6 seconds.Nice and clean, and the rates of fire make more sense in terms of segments. But wait, the PHB says that the rates of fire should be considered in terms of "melee rounds". Oh well.
OSRIC, here I come. Maybe it's clearer over there.
But first, let's look at D&D!
D&D B/X Combat Round = 10 seconds
What does D&D BX say about the combat round? Well, I don't have my Moldvay Basic Rulebook with me, but my Expert Set book does state
As in the D&D Basic rules, time in encounters is measured in 10-second rounds.Sweet, yes? Not great for my attempt to convert into HEROic D&D -- I 'd rather go with the 6 second thing so that I can just double it for the 12-segment combat turn of HERO -- but on its own, a nice measure for a combat round. No need for segments, just a small and manageable length for a combat round that fits the whole 'abstracted combat' argument in the AD&D book.
Well, in my opinion anyway.
I'm going to head over to my copies of the various retro-clones to see what they say on the matter.