A relevant point that is always true...

The achievable throughput on any connection depends critically on the equipment and configuration at each end of the pipe.

If you connect to a host that limits the datarate on any port to 1Mbps, then you'll achieve at most 1Mbps on any line.

Of course, with a high-rate service you can run multiple 1Mbps connections simultaneously, but generally they're not additive.

- Leigh