A DyingLight would fix your back-light problem, and give you adjustable brightness, but you could just hot-wire the back-light PWM from the 3.3v out on the PSU. I had the same problem with my Radeon Pro WX7100 (Polaris) card. Your 980 is getting stuck at P5 because of a power-limit in the BIOS, the easiest way to fix it is just to overclock the P5 state using Nvidia Inspector. Your welcome.
Okay, so I've started playing with Nvidia Inspector and the vBios. I can overclock the Core with no issues when it's in P5, however, the Memory won't clock past 1600mhz. If I try to move past 1600, it just resets back to the previous value.
When you said there's a power limit in the bios, are you referring to the vBios? If so, what do I need to change to fix it?
Update: I made some progress. By updating the clock states of P1 and P5 to match P0, I'm able to get the memory to default speeds of 2505, but my core is stuck at 540 without the help of Nvidia inspector.
Also, the first 5 or 6 power states were set to 1000 watts on the default rom, so I lowered all of those to 85 watts. The card seems to be respecting that as MSI Afterburner shows power limit being hit and boost clocks are reducing accordingly. I'm going to have to do some air redirection in the case. My temps slowly climb up to the mid 80's at default clocks.
Update 2: I've made a lot more progress. I now have backlight in Windows thanks to the suggestion to direct wire 3.3v to the PWM (Still waiting on my DyingLight
). I used a 6 pin PCIe extension I had to hack into the PWM signal. I ran the 3.3v from the SD card cable using a cut up USB cable, which leaves me the necessary connections for the DyingLight.
I've modded the vBios A LOT. I now get 540/2505 at boot, then I run an Nvidia Inspector profile to bump the core to the set boost clock of 1228. I reverted the power limits to stock, raised the boost limit from ~1125 to 1228, lowered the base clock from 1050 to 948.5, set the temp target to 85 C, and max temp target to 95 C (previously 101 and 102, respectively). Now my card runs at 65 C. The clocks will start at 1228 and slowly fall to around 1000. I also shunted air from the hard drive fan directly onto the GPU using an old credit card that I shaped, taped, and glued. I then used a few other old credit cards to help better direct the air across the GPU heatsink from the optical drive fan. I'm fairly pleased so far, but will be very happy when my dying light is installed.
Update 3: I wasn't quite happy with the performance of the GPU with my previous mod, so I decided to allow higher temps. I set the target temp up to 92, which allows the GPU to get to 78 before it starts lowering the clocks. I also upped the base clock to 1000, which is 50 mhz down from the stock clock. However, with the increased thermal headroom, it holds 1228, most of the time (~100 over stock boost), and will slowly fall down under extremely stressed scenarios. I saw it drop to 1190 while in a specific spot in SOTTR.
I downloaded ThrottleStop to limit my CPU (i7-2600) some, to prevent overwhelming the PSU. I have the CPU set to 55 watts with a 65 watt boost. CPU mostly stays around 40-50 watts at 3.5 Ghz. CPU temps are good during gaming, 50-60 C. PSU seemed to max out around 70 C. Everything else, except LCD proximity, stayed in the 50s. LCD proximity maxes out around 63-64C.
