DragonFly BSD

ASUS4TB

ASUS mobos and 4TB drives

It appears that numerous ASUS mobos can't handle 4TB drives with legacy partitions, even if they aren't the boot drive. The BIOS will fail to POST. It is possible that the BIOS is choking on the way DragonFly sets up such legacy partitions (creating one max-sized legacy partition, which the DragonFly kernel then ignores once it has booted and uses the whole media).

The solution is to emplace a GPT partition table on drives larger than 2TB. The ASUS BIOS appears to be able to probe large drives with GPT partition tables. You can follow the instructions from 'man gpt' to construct the partition table.