Gtx 1080 FTW memory clock @4992mhz

Solution
That would explain it! :)
It typically varies based on the card model, software, and what values the card outputs natively.
In the case of the EVGA 1080, you are absolutely correct, it didn't really come to mind! :p
Try using GPU-Z and see if that gives you a straight value, or if it is a hardware bound reading.
Under what load were these measurements taken?

Memory will not run at full speed during idle, it is extremely common to get people on this forum who wonder why their GPU is running at lower clock speeds, or their memory is at lower speeds than it says on the box, and this is due to the fact that it doesn't NEED to run at the highest speed possible to run chrome etc.
 
That would explain it! :)
It typically varies based on the card model, software, and what values the card outputs natively.
In the case of the EVGA 1080, you are absolutely correct, it didn't really come to mind! :p
Try using GPU-Z and see if that gives you a straight value, or if it is a hardware bound reading.
 
Solution