Graphics Card - AMD HD6870 Reference - No OC

AMD Catalyst Driver Version, and Driver History - 12.11 - Unsure how to acquire history.

Issue Details - CCC reports the core clock at 300mhz, rather than stock 900mhz core clock. Results in reduced performance in games - msot recently, Planetside 2. Attempted to bring the core up using AMD overdrive in CCC, as well as increases the fan speed - clicking apply yields no change. Tested with furmark in the hope that it would bump the clock speed back to 900mhz, unsuccessful. Appears to have occurred after plugging in a second display. Card also idles at 50*c, rather than the 38 I'd been getting previously.

Operating System - Windows 7 Home Premium x64 (6.1, Build 7601)

Motherboard or System Make & Model - ASUS P8Z68-V LX

Power Supply - 750W, unsure of manufacturer at this time.

Display Device(s) and Connection(s) Used - Dual monitors - Manufacturer "Technika" -

Monitor 1 (main): 1440*900, connected via VGA->DVI adapter
Monitor 2: 1920*1080, connected via HDMI 

Applications and Games - Causes performance issues in all intensive games and software, notably Planetside 2.

CPU Details - Intel i5 2500K Sandybridge - No OC

Further details incoming if required. 

Higher idle temperature in multi-screen mode is normal as the memory clock is kept at higher frequencies. And as for the core clock staying at 300mhz, make sure you arent keeping any browser windows with flash active open (like some youtube video etc.), hardware accelerated flash would force on 2D clocks, HW acceleration can be disabled in browser settings.