from page 39 of this thread on people having issues with the monitor not sleeping
"Also, update to my issue prior - I seem to have fixed the power cycling issue/GPUTweak disabling monitors on startup issue I mentioned earlier. To sum it up from the [H]ardOCP forum......
As others have said I went into the BIOS to disable the on-board GPU (i5 4670K) - the trick is to make sure you get ALL of the options in the BIOS that deal with the iGPU/IGD. I'm on a Maximus VI Hero and there are a couple different menu locatiosn and option settings that deal with the PCIe/primary display/on-board graphics that all have to be changed in order for the iGPU to completely be disabled from any access to the monitors.
Additionally, I'd run a round of CCleaner after uninstalling any utilities and proceed after the CCleaner run with a fresh install - it worked for me - no waking from sleep issues or swapping of monitor inputs via GPUTweak changes as of yet. Btw, this is all with DP 1.2 enabled and with the drivers included on the discs with the monitor installed so that Windows device manager recognizes them as LG monitors...not Generic PnP device.""
GrizzlyflameThanks but I don't have an onboard gpu. I'm still on an LGA 1366 board with an i7 950. I did a fresh gpu driver install using DDU and I've also used the monitor driver from the cd so the pc does recognize it's an Lg monitor. I am on Win 8.1. Wondering if I went to Win 7 if the issue would persist.
GrizzlyflameThis was only a single fix thus far. There are a lot of people having this issue that have disabled on iGPU in BIOS, or simply do not have iGPU. The issue is resolved using an HDMI cable but that limits refresh rate to 50Hz. I'm about to compile a Google Doc to get all this info into one place and see if we can narrow this down.
"Also, update to my issue prior - I seem to have fixed the power cycling issue/GPUTweak disabling monitors on startup issue I mentioned earlier. To sum it up from the [H]ardOCP forum......
As others have said I went into the BIOS to disable the on-board GPU (i5 4670K) - the trick is to make sure you get ALL of the options in the BIOS that deal with the iGPU/IGD. I'm on a Maximus VI Hero and there are a couple different menu locatiosn and option settings that deal with the PCIe/primary display/on-board graphics that all have to be changed in order for the iGPU to completely be disabled from any access to the monitors.
Additionally, I'd run a round of CCleaner after uninstalling any utilities and proceed after the CCleaner run with a fresh install - it worked for me - no waking from sleep issues or swapping of monitor inputs via GPUTweak changes as of yet. Btw, this is all with DP 1.2 enabled and with the drivers included on the discs with the monitor installed so that Windows device manager recognizes them as LG monitors...not Generic PnP device.""