On Monday, June 19, 2017, Theo de Raadt <dera...@openbsd.org> wrote:
> > I get the error Message that "installboot: /mnt/usr/mdec/biosboot extends
> > Beyond sector 268435455. OpenBSD might not boot." I'm dual booting with
> > Windows using Windows' boot loader first.
> You've created an OpenBSD MBR partition too far up your disk. It
> won't work in legacy mode. The BIOS won't be able to read it.
> You can try EFI mode instead.
It used to work fine for many years and upgrades. I don't think it's new
enough to have EFI.
In the worst case I'll reinstall on the backup HDD.