I've just cabled my house (Yay!). When using iperf I notice that I don't ever get a speed over about 500 Mbits/s. I know that lots of older consumer grade gigabit ethernet cards won't actually do full gigabit ethernet, I'd just like to check that this drop in speed couldn't be caused by a wiring fault. Could it?
The way to determine this is to examine interface statistics for FEC failures.
Generally speaking, 1000GBASE-T is relatively tolerant of wiring that's a little noisy, but you will see CRC32 errors - if you're getting these, especially when transferring at however close to full-whack you can get, then yes, it's likely the wiring. Otherwise, nope.
Check that the link is auto negotiated to the right speeds (gbit and full), and at both ends. I had a vender install cables recently and they Fluke validated all of the runs. I am not sure what happened, but one of the links auto negotiated at 10mbit full. Asked the vender to check it out, and he was surprised that it had any link at all. Not sure how that slipped by the Fluke, but he punched it down again and it has been fine since.