http://www.pcgamer.com/intel-now-knows-why-spectre-and-metldown-patches-are-causing-reboots/

About a week and a half ago, Intel acknowledged that firmware updates intended to mitigate security threats posed by Spectre and Meltdown were causing reboot issues on some Broadwell and Haswell systems. Intel now thinks it knows why and is making "good progress" on a solution.

"We have now identified the root cause for Broadwell and Haswell platforms, and made good progress in developing a solution to address it. Over the weekend, we began rolling out an early version of the updated solution to industry partners for testing, and we will make a final release available once that testing has been completed," Intel said today.