GRUB Disappears With Above 4G Decoding
I was fiddling with the first steps of PCI pass-through.
I have an Asus Z170-K motherboard. While in the middle of the BIOS/EFI configurations, I ran across a curious option.
Advanced -> System Agent (SA) Configuration
Above 4G Decoding
The associated help text showed the following:
Enables or Disables 64bit capable Devices to be decoded in Above 4G Address Space (Only if System Supports 64 bit PCI Decoding). note: only enabled under 64bit operating systems.
Interesting. I am using a 64-bit operating system. I probably want that option enabled. Right?
I enabled the option, but did so while in the middle of the other configurations. I immediately forgot I had toggled the option.
After a nature break I rebooted. GRUB had disappeared. GRUB still booted, which was a relief as well as curious. Just a blank black screen while GRUB timed out. Then all returned to normal with the boot stdout.
Further confusing me was I tried a full power down. On restoring the power switch the system did not automatically power on. I had configured the BIOS/EFI Restore AC Power Loss to Power on.
I was dumbfounded for a bit because I forgot about that option. When I disabled the option GRUB returned and Restore AC Power Loss worked again too.
Some web surfing indicates this option has something to do with multiple GPUs. The option seems popular with cryptocurrency mining nuts (people who think mining is a replacement for winning the lottery and pay more in electric bills than they actually earn from mining). Seems the MSI folks even label this same option as Above 4G Decoding/Cryptocurrency Mining.
I think the result I saw is I use the on-board GPU. The on-board GPU is ignored until the kernel starts booting. That BIOS/EFI option enables using GPUs above the 4G address space but somehow affects the on-board GPU. Curious the system still booted.
The Twilight Zone theme is playing.
Never do two things at once with computers. Something always breaks.
Posted: Category: Usability Tagged: General
Next: Log Spew From sysctl