Originally Posted by jazznaz
As far as I understand it, the secondary core is only clocked up to the maximum when playing a game that supports crossfire in fullscreen mode. Then the core kicks in at full clock and memory speed. Since BOINC does not emulate this scenario, you're stuck at 507Mhz on the secondary core unless you play around with it.
Did you give gputool a go? It allows you to set the 2D and 3D clock/mem speeds independantly
Download and install GPUTOOL (HERE
Then start it up and go to the "Fan Control" tab and set the fan control option to "hardware" and at the bottom set the "mode" to "Fixed".
Then you'll see in the grid area a line with2 dark points on it - drag the first/left point all the way to the bottom left (around 10C and 0%) and then drag the second/right point across the top to 60C and then down to 80%.
This will make the fan come on 100% above 60C and then scale down the fan's speed to 80% just under 60C and from there it'll scale down the fan's speed further as the card's temp drops further. Play around with it and you should find a good compromise between temps and fan noise.
Then go back to the "Clocks" tab.
Now before you adjust the clocks, at the very top you'll see a drop down list that lists your GPU. If you have a card that has 2 GPU's then that drop down list will list both of them. Select the first card.
Just under where it lists the tab names, you'll see a second drop down list that lists your card's 2D/3D levels. Select the first option (most likely "2D Clocks") and then under the drop down box, set the sliders to the OC you want to run in 2D and then click apply.
Then go back to the second drop down list and select your card's next 2D/3D level (most likly "3D Clocks") and again set the sliders to the OC you want to run and then click apply.
Keep repeating until you have set the speeds you want for each of your card's levels. And then in the very top drop down list again, select your next GPU and repeat.
If you wanted to ensure that your card operates at the speed you want in BOINC, try settings all of the 2D/3D levels for both GPU's listed in the very top drop down list to the speed you want.
750/900 are stock speeds for a single 4870 so they should be a good starting point.
With that all sorted and all speeds set in GPUTOOL for your card's 2D/3D levels, then start up Open Hardware Monitor (HERE
if you don't have it) and check the speeds of your GPUs and also check the temps.
Hope that works for you