ATT works great! My HD6870 finally shows some power.
You can create a 3D clock profile and then use it in a game profile that will only set the clocks to the 3D setting when you launch "launcher.exe", then set it so the clocks return to 2D levels when you close the game.

I will try the ATI Tray tool if the patch does not solve the problem. Will let you all know the results in this post.

ATI tray tools, 870MHz on 4890 fixed everything: enjoyable (patched) game, 50fps over sea, 25 over land, everything high in 1680x1050, no AA yet.
Looking at beta patch thread, most if not all ATI owners are disappointed, Nvidia see improvement -> points to GPU speed being the limiting problem on ati cards ...

Well the beta patch did not fix the idle step up problem at all. Very dissipointed. Other than the stuttering this has to be the biggest problem. Has it even been addressed at all?

Will try ATI tray tools now. And hope it doesn't crash my machine like it does with my friends.

the idle step problem will be address in the final version

This is what's worked for me:
After doing that, my clocks have been at full speed.

EDIT
Having received today's patch, this no longer works.

So how do we set up a profile with ATT?

After many hard crashes I got ATT to keep my card in a stepped up state. This allowed me to play the game.

Something I am keeping an eye on though is the card temps while running ATT. I am not sure yet if ATT is using its own temp/fan profiles. As the card is getting hotter than it normaly would say playing ARMA2. So I have bumped the fan speed up a little to be safe.

ATT is a temp fix if you have this issue. Also a way to stop the hard crashes in ATT is to switch the voltage option to a higher voltage. This is found in the same screen where you set the clock speed.

Hi,

I have also 4890 and trying to get the max out of it so could you post some (AtiTrayTools) setup specs since it crashes my computer every time I try to set it up...

Thanks

Stock speed of my 4890 is 850:975. It crashes if I overclock it usually.

Try making a profile for ATT for this speed.

It's no go with the ATT profile-thing :( pc freezez when launching the profile.