My mother lives just up the road (on the same exchange) and has a Windows Vista system running broadband with Waitrose.com. She's pulling 6.1MB download and 3.7MB upload speeds! Unless I'm overlooking something, mine has gotta be an ISP fault, no? Otherwise, is it possible my system has been changed (hijacked?) in some way to account for the slowdown?
"Just up the road" can make an awful lot of difference. For example, between her home and yours the cable could be bent a bit too sharp around some corner, or it goes a bit close to a power cable, or some digger came a bit close to it. It's the quality and the length of the cable between the exchange and your home, and how much noise it gets from the outside, that determines the line speed.
Anyway, the connection speed is negotiated between the ISP and your ADSL modem. There is _nothing_ that the Mac or Windows can do about it. If you have a MacBook, take it to her home and plug it in; you will get exactly the same speeds as she gets. If she has a laptop, take it to your home, and it will slow down to your speed.
Anyway, I am switched from Orange to O2 now. £12.50 a month (£7.50 if you are a phone customer), "up to 8 MBit" which turns out to be 2 MBit for me, "unlimited" which is probably 10 or 30 GB but nobody can or will tell you; plenty to download the occasional iPhone SDK. The important thing is: It works with no interruptions at all (so far). I never cared too much about the speed, but if you don't have a stable connection, that is really really annoying. Are you just concerned that your number "2 MBit" is less than your mother's "6 MBit" or are there things that are running too slow? Very often it would be the server (like if MacRumors takes 10 seconds to reply then it doesn't matter how fast your line is); in my case it was bloody Orange disconnecting every five minutes. You could open "Activity Monitor", switch to "Network" and check how much data is actually transmitted and whether it comes anywhere close to 2 MBit = 250 Kilobyte per second.
That's not strictly true in all cases, although in this case the Mac is not the likely problem. Your TCP settings do impact the delivered speed of the connection, including speed tests. For general cases, OS 10.4.6+ or 10.5 have very decent defaults, although I usually increase the TCP receive window on 10.4.x.
Your Mac does _not_ influence whether your line has 2 MBit or 3 MBit per second. What the computer can do is to influence how efficient these 2 or 3 MBit per second are used. You _could_ probably set up a Mac to run very slowly even with 8 MBit per second, but the line would still be 8 MBit.
