It would be the understatement of the year or at least the week to say that the work did not go as anticipated. The machine I was going to use as a basis for comparison, it also had an old BIOS and given it was the same as the other machine that kept losing it’s fan profile, I decided it was best to upgrade it as well.
When I upgraded the BIOS it returned to the default settings which meant that I had to determine good settings from scratch. While I was doing this another machine crashed.
I don’t really know what caused the crashes but I found a number of problems. For one thing VTd instructions were not enabled but should have been since we have kvm/qemu virtual machines on these boxes. Not having it enabled isn’t a show stopper but it causes Linux to more work to perform I/O in a virtual machine.
Then I found an issue with an item that allows full 64 bit address decoding for I/O devices. For some reason this breaks the built in graphics of the i7–6700k causing instability.
I now have all the machines on current BIOS, ran some torture tests on the CPU and they ran clean. So we’ll see how it goes. I had to slow down the CPU’s slightly on two machines to get them to complete the torture tests without error.