[Solved] Sleep problems with Gigabyte Z97X motherboard

[Zim]

I'm posting this in an effort to help anyone who might encounter the same issue...

I recently put together a new build with an Intel i7-4790K CPU, a Gigabyte GA-Z97X-UD3H-BK motherboard, and Windows 10. Windows 10 prefers Sleep as its low power state but my new system did not. Invariably it would crash going to sleep or waking up. The Windows Event Log would display various bugcheck codes that indicated either memory or video issues. After investigating many potential causes I discovered the problem...

The i7-4790K, being a Haswell CPU, supports a newer power state(s) from previous CPUs... namely the C6/C7 states. Gigabyte have chosen to enable these by default on their motherboard. This is not good if, like mine, your power supply is not Haswell certified. I'm guessing that there are many older PSU's out there that will work fine, but my XFX TS 550 would not. There were two fixes for me that I have verified: either disable the C6/C7 power states in BIOS, or use a Haswell certified PSU.

 

[Zim]

An update on this. The problem was not the PSU since replacing it did not fix the issue. I never got to the bottom of it but the main suspect is the motherboard. I'm guessing that it's a BIOS issue but Gigabyte stopped supporting this board pretty quickly so a solution is not on the horizon. I'll try MSI next time.