Yes , you have a NIC let's say NIC A that is 10/100/1000 and the other NIC B that is 10/100.
Apparently NIC A seems faster, but it can only utilize 1000 bits per second if it was transfering from another 10/100/1000 NIC. You don't have to do anything, it's all automatic.
Remember 1000mbps is only the throughput and is not the actual download speed or upload speed. Many people use the equation mbps/8 - network congestion - other things and so on to determine download speed but it's not really quite accurate or do I suggest you used the equation because I have no idea what I was thinking LOL.