Hey all I'm having a lot of trouble finding info on this. I just built a gaming machine with a Z170 FTW & core i7 6700K. It's been running fine for a few weeks but now does 5 beeps after all the short beeps then boots normally and the machine seems fine otherwise. I also have 3200Mhz RAM that's showing up at 2166Mhz in automatic mode. I tried resetting the BIOS to optimized defaults, that didn't work so I tried updating the BIOS to the latest version, and the problem continues. Any ideas what this could be? During the 5 long beeps the LCD display on the motherboard reads POST code 96. I looked it up and that is "PCI Bus assign resources". My back-lit keyboard also powers off and back on again right before it starts to boot into Windows 10. It didn't do that before. Thanks for any help. 

Welcome to the forums,
 
Normal..After the initial beep/s, additional beeps correspond to the number of USB devices that are attached.
 
You can perform a Forum Search for 'Z170 beeps' and find results such as here and here and here.
 
You can disable the Speaker Beep in the BIOS Boot menu if you want to.
 
You can set your RAM to use it's X.M.P Profiles, if any..Or..Manually set the manufacturers rated Frequency, Timings and Voltage in the BIOS (best)..The manufacturers specs are normally on a sticker affixed to the RAM, or on their website.
 
When RAM is set to Auto in the BIOS, it will only run at the JEDEC SPD speed (for compatibility purposes) which can be lower than the full rated speed..Full speed usually requires an X.M.P. Profile to be set, or the RAM to be manually set.