I have now gone from 160 mb/s to 40 mb/s and I cannot figure out why this has made me so much slower? I used to wire up my old MBP which had the ethernet port and that was a stable 160 mb/s but this adapter has quartered the speed of my connection on this newer model.
This is a very interesting thread for me.
So many places that things can go wrong, the quality of the copper as
bobtomay said is probably the first place I'd be waving a disapproving finger, however, it could also be the ASIC in your switch/router, we received a batch of Cisco switches with faulty ASICs which caused the craziest list of problems. Now you're probably using the Virgin Media router (huge assumption on my part) which should not have the ASIC quality of a Cisco switch, but even so, 40Mbps would be pretty shocking and I'd be surprised if the most basic of QA checks let that one through.
Anyway, lets look at testing the actual communication in your home, do you have another computer inside the house that has the ability to use both wireless & wired?
This second computer does
not need to be a Mac.
You want to install something called iperf
iperf or iperf3 and install it on both machines.
This is a super simple application that will dump a bunch of UDP or TCP packets into your network, you use one device as a server and one device as a client, this thing will burst enough data for you to see what throughput you achieve.
I would try a bunch of tests if I were you, so wired-to-wired, wireless-to-wireless, wired-to-wireless, etc etc etc (also, if available, repeat the tests with different copper, you might be surprised at how big a difference this cable can make).
This will give you a real idea of what the hardware can deliver. The least productive test will be the wireless-to-wireless as your wireless AP (presumably the Virgin modem) will be the bottleneck as the way wireless works means that the device will struggle to give both clients perfect throughput at the same time.
The commands for iperf are super simple
Code:
iperf -s
iperf -c ip.address.of.first.computer
Why is there a difference between wired & wireless? It may be the thunderbolt adapter, but it may be the VM Router, it may prioritise the wireless traffic in which case I would expect the wired-to-wired tests to see the same limitations.
I'm not offering any hard and fast answers here, just a little more troubleshooting to help you pin down the cause of the problem.
Some really simple OS X instructions for iperf testing:
Test your home network and much more detailed instructions on the iperf command set can be found here:
clicky.