Out of the box most routers end up splitting the traffic equally between all the computers connected to it who want access. It has nothing to do with master computers or anything like that - in a corporate environment maybe so if data goes through one computer to get online but this doesn't apply in your case.
Having said that, having Googled the model, it would appear this router has issues with wireless connectivity anyway which may explain why you have the problems you do wireless. Also don't forget if the first computer is downloading your connection would be slower anyway, and vice-versa.