Yea I thought that would work too, unfortunately it doesn't.
At least with the bios that I've tried, which were the reference 5870 bios from Powercolor and the PCS+ 5870 bios - unchanged, none of them worked.
I even tried modifying the voltages on the 5870 bios to match the voltages of my 5850 PCS+ and it doesn't work, it still is unstable when pushing for 1200mhz memory clock speed. Although works fine if you don't push it.
It seems that the bios doesn't really manage much.. well at least not the memory timings... or the voltages.
Odd, being the bios I thought it would be just like the bios for a motherboard I guess it's architecture is really different.. that is... it is much simpler and manages a lot less.
Well either that or the 5870 bios is just different from the 5850 bios. I just hope RBE gets some sort of memory timing feature sometime in the near future.
Edit: It is nice to see that I am not the only one with the card though, it seemed like I was the only one using the 5850 PCS+, which does have a great cooler, just wish it overclocked better.
Oh and wait for when I do a vGPU voltmod, I have a feeling that is why it doesn't overclock too well.
Seeing as how all that msi afterburner changes with the reference cards is the vGPU voltage it seems the vGPU voltage may have more to do with the limitation than the vMem voltage.
Now if only uPI-semiconductor would release info on the uP6219!