TL;DR: My laptop starts ~20x slower than normal. Booting Debian hangs
before the kernel starts. Windows 10 boots slow, but then works fine.
Hardware problem?
More details:
I bought a Lenovo IdeaPad Flex 5 in April 2019. It came with Windows 10, I
installed Debian buster on it (dual-boot with GRUB 2). Worked flawlessly
(with secure boot!) for ~8 months.
In January 2020 after some reboot for the first time it started slow, and
hung while booting Debian. Windows boots slow too, but once it's up it
works just fine. BIOS SETUP UI is also very slow.
Since it might not be obvious what I mean, here is a recording, with
detailed timeline in video description:
https://youtu.be/HCgO9UblqtI
After a few reboots it came back to normal. Then this effect came and went
a few times, and now it's here for good. I cannot boot Debian at all. I
tried leaving it booting overnight once and it didn't show any progress.
Windows still works OK. Updating BIOS to the most recent version did not
help.
I asked on the Polish Lenovo support forum
<https://forums.lenovo.com/t5/Laptopy-IdeaPad/Flex-5-drastyczne-spowolnienie-bootowania/m-p/5010338?page=1#5037024>,
the response was that "this model does not support dual boot (sic!), they
have had no similar reports in the past, and installing Linux on it might
have caused the problem". I'm shocked.
Initially I thought this might have something to do with Windows updates,
because on the first occasion it seems to have disappeared after Windows
completed its scheduled update. But now I think it was just a red herring.
In my almost 30-year experience I have not encountered a problem which does
not go away after a cold reboot, but does go away after Windows starts :-O
My only theories now are:
- a hardware problem (but why does it go away once Windows boots?)
- a botched CPU microcode update (but I suppose there are checksums which
would prevent it from happening, so not likely).
Any thoughts?