Note: I have ArM4. I don't know if there are any difference and/or explanation in ArM5 for this issue.
In ArM4 you can walk 9 + Qik paces per combat round. If you'll attack on this round you can walk only the half distance. There are other formulas for other speeds.
My doubt is about mages. I don't know how many paces should a mage walk and then cast a spell. I think he need all the round to cast a spell, but he can walk too, since there are a concentration roll for this situation. But if he passes his concentration roll how many paces he can walk while he cast a spell on a round? He can walk 9 + Qik paces as ussual? Or the half?
It's been awhile since I looked at Ars4, but if your right about the 1/2 during combat. Then I'd say 1/2 during combat. That's when the walking occurs. Do you forsee problems with judgement. Successful Concentration rolls allows 1/2 walk during combat?
The 4th ed rules say nothing about half-walking for spell-casting.
They do have increased Concentration rolls necessary for increased movement:
(4th ed, p 73-4)
Concentration
[i]"It takes concentration to cast a spell. If anything distracts you while you are casting, you must make a Concentration roll to maintain the spell. If you ever fail a Concentration roll while casting or maintaining a spell, the...* spell automatically fails (though you must still roll to determine if you botch the spell, and you receive one extra botch die if you do). If your Concentration roll ever botches, you automatically lose a Fatigue level.
The ease factor when making a Concentration roll is dependent upon the type of distraction. The type of die rolled is always a stress die, and it is modified by the caster’s Concentration and Intelligence. Sample ease factors are listed on the Distraction Table. When more than one situation applies, use the largest ease factor."[/i]
Of the 6 "phases" of 4th ed combat, the 1st is movement, the 5th is magic- no mention is made in either section of the other. (The last phase is "fatigue".)
Since the chapters on Magic and Combat are distinctly separate, and no mention in either is made of limitting magi who are casting spells in any way, I've never seen (by the rules as written) cause to do so.