I would agree to it coming near 280X stock speeds. Just did some benching on my 270X Devil and a VisionTek 280X. For FFXIV benchmark, my card at 1260/1565 scored 90% as high as the stock 280X.
It is safe to say that a well clocked 270X can easily match/best a 7950/280 at stock speeds.
P.S. You must have one hell of a 270X to hit 1350 Got some pics?
What card/cooler is that to not exceed 75C at that voltage/clocks and only 50% fan speed? My 270X at 1260/1565 1.3V was hitting 72C in 3DMark11 with fans at 80%
I have a regular MSI 270X gaming. For some unexplainable reason i'm able to push 1.4 VDDC through the card, so that explains pretty much why i can clock the card so high.
and a 3DM11 result from the run i just did with a very bloated windows that hasn't been rebooted in a few days.