I know the specs say it's designed for 1 Gbps has anyone ever tested whether it can do more?
IE. Can it do 4 Gbps? 5 Gbps? Up to 10 Gbps? Any real tests that show this?
Ethernet is not WiFi. Nor ADSL.
With WiFi (and with ADSL), both sides do a little testing to see what speeds are manageable without too much bit-errors and frame-drops. And then they settle at a particular speed.
With Ethernet, it's simpler. The speed is fixed. There are different generations of Ethernet. 10 Mbps, 100 Mbps, 1 Gbps, 10 Gbps, 40 Gbps and 100 Gbps. Both sides can do one or more of those speeds. There might be a little auto-negotiation to see which speed the cards on both sides support. And then they transmit at the highest speed both cards can do.
If the cable between the two isn't good enough, there will be bit-errors. And maybe frame-drops. But both sides keep transmitting at the same speed. They won't adapt. The won't go from 10 Gbps to 7 Gbps and then to 3 Gbps to see if that gives less errors.
Another thing you should understand: the speed that is guaranteed for a particular type of cable is for a specific maximum distance.
Example: 1 Gbps over Cat-5e is supposed to work over 100 meters max.
https://en.wikipedia.org/wiki/Category_5_cable#Maximum_cable_segment_length
Another example: 10 Gbps over Cat-6 is supposed to not go over 55 meters max.
https://en.wikipedia.org/wiki/Category_6_cable#Maximum_length
So can you do 10 Gbps over Cat-5E ? Probably if your cable is only 10 meters long. Longer ? I don't know. A little googling gave me this page:
http://www.kit-communications.com/FAQCat5evsCat6.htm
The claim here is cat-5e can do 45 meters 10 Gbps.
Cat5e:
Gigabit Ethernet up to 100 meters
10 Gigabit Ethernet up to 45 meters
Cat6:
Gigabit Ethernet up to 100 meters
10 Gigabit Ethernet up to 55 meters
Cat6a:
Gigabit Ethernet up to 100 meters
10 Gigabit Ethernet up to 100 meters
If that is true, that's good news. I got cat-5e under the floor (concrete) in my house. No way I can replace it. But it's 20-25 meters max. Looks like I can use 10 Gbps in the future, without pulling new cables. Nice.