Can anyone explain me what "Compute units" are? They seem to be different on my 2 cards? I believe it depends on the GPU manufacturer?
http://imgur.com/a/ptDWr "Compute Units" is an AMD marketing thing where they tried to count CPU cores and clusters of GPU cores as being equal for marketing purposes.
It gets REAL irritating on their A10 series APUs.
For a GPU, a "Compute Unit" = 64 "cores", so one of your Tahiti cards is a "X" the other is a non "X" - 280x vs 280 or 380x vs 380.