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I have a laptop, Asus X401U, that came with Windows 8. I've been trying to switch to Linux via DVD, read online tips about how to get to the BIOS, and got stumped after UEFI (my reference is this guide: My Boot Tab isn't the same. It's more like this one here (If USB is not listed in BIOS as a boot option, does that mean the machine can't boot from USB?). I'd gone to a tech already and he told me that the DVD drive I use, which my computer can read otherwise, doesn't register on the Boot Options. He'd gotten a flash drive and it worked. I'm not a techie, so I don't think I quite get what "Unfortunately with Windows 8 you can not boot from bios" means (in the second link) - does that mean there's no way at all for me to remove Windows 8 and replace it with Linux?


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First, let's clear up some terminology issues:

  • Firmware -- This is a type of software that's built into or loaded onto a device. In the context of computer motherboards, the firmware controls the first part of the boot process: It initializes hardware, loads a boot loader from the hard disk, and transfers control to that boot loader. The boot loader may then call upon firmware functions (such as disk-read functions) to help it do its job.
  • BIOS -- This term has become used in so many conflicting ways that it's becoming next to useless, IMHO. Personally, I use it to refer exclusively to the original IBM PC Basic Input/Output System (BIOS) or its modern derivatives. This is a class of firmware that's been in use for over 30 years. It has a number of embarrassing limitations on modern systems, and so is being phased out. Many people, however, (including most PC manufacturers) use the term "BIOS" as more-or-less synonymous with "firmware," at least in the context of motherboards. This leads to confusion because it becomes unclear if the reference is to firmware generally or to BIOS (as I use the term) firmware specifically. Your original question uses the term in both ways, which illustrates the confusion potential inherent in this term.
  • EFI -- This is a (relatively) new type of firmware, intended to replace the BIOS (as I use the term). EFI is big and has a number of modern features that make it more flexible on modern hardware. A variant of EFI is UEFI, which is basically EFI version 2.x. The vast majority of modern PCs use EFI firmware, and Microsoft requires that computers that ship with a Windows 8 logo boot in EFI mode by default. Thus, your new laptop almost certainly boots Windows in EFI mode.
  • CSM -- The Compatibility Support Module (CSM) is an optional UEFI feature that enables it to run BIOS boot loaders, and hence to boot OSes designed for BIOS-based computers. Most modern UEFIs include a CSM.
  • Legacy -- In this context, "legacy" refers to booting in BIOS/CSM mode.

An OS typically includes boot loaders to enable it to boot in BIOS mode and/or in EFI mode. (Separate boot loaders are required for each mode, although some boot loaders, such as GRUB, can be built to support both boot modes separately.) In the case of an EFI with CSM, boot options you can set in the firmware setup screen and/or options you can select at boot time using the firmware's built-in boot manager enable you to select whether to boot an EFI boot loader or a BIOS/CSM/legacy boot loader.

Now, to your question: The "Unfortunately with Windows 8 you can not boot from bios" comment does not use "BIOS" in the sense of "firmware," but in the narrow sense of BIOS/CSM/legacy boot mode. It's also not entirely accurate; Windows 8 can boot in BIOS/CSM/legacy mode. What's true, though, is that the pre-installed Windows 8 on new computers is typically configured to boot in EFI mode, not in BIOS mode. It's also best, on a dual-boot computer, to boot both OSes in the same mode. Thus, you want to find a way to boot Linux in EFI mode.

If your firmware isn't giving you an option to boot from your DVD drive, then that sounds like a firmware bug, or possibly a problem with your DVD. There may be a workaround for this, but it's probably easier to copy the Linux distribution's installer to a USB flash drive and try booting from that, ideally in EFI mode. (Sometimes you'll see multiple boot options for one device; select the one with "EFI" or "UEFI" in the description to boot in EFI mode.)

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Hi, I'm the original poster. Thanks for this! – user250628 Sep 4 '13 at 2:11

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