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Thread: Installing Windows 8 with CSM disabled (full UEFI)?

  1. #1
    rseiler is offline Junior Member
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    Default Installing Windows 8 with CSM disabled (full UEFI)?

    My theory about this is that the BIOS has an issue, but I could easily be wrong, as there are a lot of settings in it. Here's the issue:

    On a Win7 machine, I dl'd the retail Win8/Pro x64 from MSDN (it's called en_windows_8_x64_dvd_915440.iso) and burned a DVD with PowerISO.

    The Win8 machine to-be: Asrock B75M-DGS (Bios 1.20), with CSM disabled. Blank SSD. It will not show the above DVD on the boot menu when booting the system. The boot menu is entirely blank, in fact.

    When CSM is enabled (not that I wanted to install that way), it does show up.

    When CSM is disabled again, and I use a specially-made USB stick, I'm able to choose the Win8 install and proceed. I did it this way, but thought I'd report my experience with not being able to use the DVD.

    I've read of an issue like this when using a DVD created via the Win8 Upgrade Assistant, but this isn't that.

    I poured over UEFI to see if there were any further settings pertaining to this, but I don't think there are. Based on another thread, I did try using Launch EFI Shell from filesystem device, but, according to the manual, all it does is search for a file called Shell64.efi, which doesn't exist (why wouldn't it search for bootx64.efi, which does exist?). If, as some of the threads mentioned, it let me open a UEFI command prompt, I apparently could have typed this to get the DVD to boot (possibly fs1: instead), but it never let me.

    fs0:
    \EFI\BOOT\BOOTX64.EFI

  2. #2
    parsec's Avatar
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    Default Re: Installing Windows 8 with CSM disabled (full UEFI)?

    I installed Windows 8 from a USB flash drive in UEFI boot mode by setting Secure Boot to Enabled. Didn't change CSM at all.

    So you haven't enabled Secure Boot and installed the security keys, an option in the UEFI? My installation worked fine, GPT partitioned, and when complete the CSM option did not exist in the UEFI.

    I bet your installation would have gone fine with CSM enabled, unless your UEFI/BIOS did not have the Secure Boot option.

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    rseiler is offline Junior Member
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    Default Re: Installing Windows 8 with CSM disabled (full UEFI)?

    The UEFI installation did go fine--with the USB key, my only option. CSM is enabled by default on my board, so you definitely have to disable it for a UEFI install.

    Before v1.20 of the BIOS, the situation would have been different, as you're saying CSM didn't exist back then. That makes sense, since it's not in the manual either (the manual is several months old). Secure Boot isn't listed in it either, so I had neither. But the BIOS/UEFI update in December changed all that, and both options (and more) are there now, making it essentially identical UEFI-wise to the R2.0 model, which is the manual I referenced for some of the newer settings.

    With no CSM option, as you found, then choosing a "UEFI:xxxx" boot item and installing via it must have been the only way to declare that you wanted a UEFI install. Secure Boot, according to the above article, should be enabled only later, but clearly based on what you said it's OK to enable it up front.

    But the mystery of the DVD remains. Has anyone actually seen a "UEFI:xxxx" in the boot menu for the Win8 DVD (or Win7, I guess, but I didn't have it to try, so I don't know if it would have shown) on the current BIOS?

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    parsec's Avatar
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    Default Re: Installing Windows 8 with CSM disabled (full UEFI)?

    I'm guessing the article you read assumes (perhaps correctly) that enabling Secure Boot also installs the security keys (GUID's), which is not how my boards UEFI works, the security keys were installed by me (with the available option to do so) after the UEFI OS installation. That does follow the model I read somewhere else about UEFI boot, with the Setup (for installation) and User (for running in secure boot) modes, which were displayed in my board's UEFI.

    You may be correct about selecting the "UEFI:xxxx" boot item as the way to specify a UEFI install. Gosh I wish there was a clear and correct guide about what at least should be the correct implementation. Not saying ASR is wrong, I just don't know!

    Yes, the DVD as a UEFI boot entry option remains a mystery.

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    Ácode is offline Junior Member
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    Default Re: Installing Windows 8 with CSM disabled (full UEFI)?

    Quote Originally Posted by rseiler View Post
    EFI\BOOT\BOOTX64.EFI
    Did you check your DVD to see if the above directory and file was on there?

    Bootx64 is an application while shell64.efi is like a mini OS with inbuilt commands. Think of it as something like DOS but for EFI.

    It is possible to do a UEFI install with csm enabled onto GPT. Maybe this would work to get you started then switch over the other stuff later. I do not have the same board as you so can not help much but with Z77 Pro 3 and BIOS 1.90 mod I do get UEFI DVD and/or Legacy DVD depending on settings.

    Here is an example of the DVD options (ATAPI) attached to intel SATA port in RAID mode.
    Name:  BIOS.png
Views: 12271
Size:  16.6 KB

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    rseiler is offline Junior Member
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    Default Re: Installing Windows 8 with CSM disabled (full UEFI)?

    Yes, the disc does have that, so I think we can take the help screen in the BIOS at its word: it's not exactly what it was looking for.

    What does have shell64.efi then if not Windows media?

    Huh, I never would have imagined that it could be done with CSM enabled, since why does the CSM option exist then? The above article says that it "makes the motherboard actually look like a BIOS system, allowing it to boot from NTFS and MBR disk--but you lose the UEFI features and are essentially just using BIOS." Yet, if CSM is enabled, and you somehow get a UEFI DVD boot menu, installing Windows then is as if CSM was disabled?

    I just assumed that Windows installs differently at a low level (beyond the GPT formatting, which you're saying happens even with CSM enabled as long as you choose UEFI on boot), with CSM disabled vs not. I guess you could test that theory by later disabling CSM and attempting to reboot Windows. The result may not be pretty.

    Also, you mentioned that you could get a legacy DVD boot menu (as opposed to UEFI) with certain settings. Do you recall which ones? Because whatever that is seems to be the decider in whether you get a traditional install vs a UEFI one, not CSM.

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    parsec's Avatar
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    Default Re: Installing Windows 8 with CSM disabled (full UEFI)?

    reseiler, I just happened to do another Win 8 UEFI install on my board, starting in standard BIOS emulation/CSM enabled. Recall that the CSM option is displayed in my BIOS/UEFI until a final boot with the security keys installed, as they call it in the BIOS.

    I tested disabling CSM while it was still available, and the reboot failed. I should say POST failed, as I got a three beep POST error. I had to enable CSM to boot successfully. Later, the CSM option was again gone from the UEFI (ATAPI screen on my board.)

    I just mention this as an FYI, not that it matters for your board, just another seemingly odd difference. Don't you hate it when you don't really know what's going on...

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    Ácode is offline Junior Member
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    Default Re: Installing Windows 8 with CSM disabled (full UEFI)?

    Quote Originally Posted by rseiler View Post
    Yes, the disc does have that
    Okay, I asked because if it were missing then that would result in the BIOS not showing it as a UEFI boot option.


    Quote Originally Posted by rseiler View Post
    What does have shell64.efi then if not Windows media?
    You can place it on any FAT32 media such as a USB flash drive, the BIOS should look for it. AFAIK some BIOS also have an in-built shell. There are different pre-built versions around, if you google "shellx64.efi" and "download" that should get you some links to try.


    Quote Originally Posted by rseiler View Post
    Huh, I never would have imagined that it could be done with CSM enabled, since why does the CSM option exist then?
    A quote from Compatibility Support Module - PhoenixWiki
    Quote Originally Posted by Compatibility_Support_Module
    The CSM operates in two distinct environments:

    • Booting a traditional or non-EFI-aware OS.
    • Loading a UEFI-aware OS a device that is controlled by a traditional Option ROM.
    For instance with legacy you might possibly load a RAID option ROM, video ROM, PXE ROM and so on, EFI can have it's own drivers which which will work more efficiently with the EFI BIOS. By disabling CSM your asking to use those EFI drivers instead of the 16-bit legacy OROMs.


    Quote Originally Posted by rseiler View Post
    Also, you mentioned that you could get a legacy DVD boot menu (as opposed to UEFI) with certain settings. Do you recall which ones? Because whatever that is seems to be the decider in whether you get a traditional install vs a UEFI one, not CSM.
    I do not know what you specifically have with your BIOS but it might have options to choose whether to show only UEFI boot devices, only Legacy boot devices or both.

    Something also to consider is the boot options fast and ultra fast. These affect the way the BIOS interacts with UEFI booting but I do not know the specifics, maybe try with disabled if having problems (parsec?)

    IMHO UEFI really has a lot of promise but is still at a stage where some things need to be ironed out and some of the older compatibility dropped, which might take some time. For instance AsRock has not gotten around to putting the RAID config menu in my Z77 Pro3 as yet, video GOP support from Graphics card manufacturers. It is still "work in progress" for a lot of systems.
    Last edited by Ácode; 02-08-2013 at 11:20 AM.

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    Default Re: Installing Windows 8 with CSM disabled (full UEFI)?

    I agree with ucode, that UEFI booting and all its potential has not been realized in even in the PC enthusiast community, since we have only begun to really use it. Also, in our plug-and-play PC world, we don't spend the time to study how it all works. But I will say finding a good guide in one place on "how it all works" is not easy, I have yet to find one. Plus as we have seen just in this thread, the implementations of the setup for UEFI booting vary between boards, with little to zero documentation on it.

    Part of the "decider" or deciding depends upon what is presented to the BIOS/UEFI. As was posted earlier, in the boot listing we see "USB" and "UEFI" entries for the devices. I have a bootable USB flash drive I created (from a guide) for installing a UEFI booting Windows 8 installation, which can also be installed in the usual BIOS mode. If you look at the folders and files on the flash drive, you'll find files with a ".uefi" extension on the file name (like .exe is the file extension on an executable file.) I assume something in the BIOS is scanning the files on the devices and finds these file types, so can then display them, and use them for their intended purpose. Choose the UEFI device (or part of it) and you get a UEFI installation. Choose the USB device (default or standard I assume, but a non-intuitive name) and you get a standard BIOS (non UEFI) installation.

    The guide I used described setting up a Windows 7 UEFI bootable USB flash drive, but a certain .uefi file had to be moved from one to another specific folder before it would work. That implies the decider expects a certain layout of folders and files, which makes sense. How much if any of the decision process is determined by BIOS settings is one of the puzzles, but in one case we had CSM disabled, while I had Secure Boot enabled, and disabling CSM failed on my BIOS.

    Regardless, if we had explicit instructions, or a standard, we would at least know what we should do, or how it should work. I've read other manufactures boards have better labeled options for this. So we may see the marketplace fixing this in the near future.

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    rseiler is offline Junior Member
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    Default Re: Installing Windows 8 with CSM disabled (full UEFI)?

    Lots of new information to parse above. I'll just touch on a couple for now:

    -So Windows does care, post-install, whether CSM is changed. Good, because if it didn't, then the idea that Windows installs differently depending on the state of that option would have gone flying out the window. I always expected that it would care, like it does if you flip AHCI post install, though probably in a much more encompassing way.

    -I've never made a Win7 UEFI bootable USB drive, but I did make a Win8 one, and (after the FAT32 formatting), it's just a straight Xcopy of the files, no special arrangement of the files once there. It does have several *.efi files in \efi, not that Asrock cared about any of them when it looked at the very same fileset on DVD (hmmmm).

    Looking at Win7 now, which I didn't try on this board, it doesn't have any *.efi files at all, so I can see why there might have to be something special done there, though with a folder called \efi you would think that it would work as is regardless.

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