Connection Speed with Router

I am going to be buying a router that will share an internet connection between three computers. Before I buy, I would like to which of these scenarios apply, as I am a bit puzzled :):

1. The connection speed is always 1/3 of what it usually is, even if the computers are off.

2. The connection speed is only 1/3 of what it usually is if all 3 computers are on (but not nesseccarily using the internet).

3. The connection speed is only 1/3 of what it usually is if all 3 computers are viewing web pages etc.

4. The connection speed is always at the full speed at all times no matter what, between all 3 computers.

5. Something else.

Basically, I would like to know how the connection speed changes. What does it depend on etc?

I hope that made sense - I just don't want if to be always 1/3 normal at ALL times.

You will always have the same total connection speed. E.g 60kb with a 512k connection. Depending on what the computers are doing changes how much bandwidth is allocated to them. It just gives each computer the bandwidth it demands. So if someone is viewing a web page it needs less bandwidth than if someone is doing a download. The total speed can not go over the top speed of your line.

do yu have QOS on in the network properties?

I haven't yet brought this router yet. Go to "USB modem routers", to see what I might buy. I have decided to stick with what I have now, and if I decide I really need a router, I'll get one then. At least I've researched it now, and know what to get if that situation arises :).