970m pro3 disable csm = no video

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   installed this board in place of a bad one in oem machine.  Reinstalling windows 8.1 x64, it says can't install to the disk bc it is of the gpt type.   Well, this is an EUFI board and 64 bit windows, so that shouldn't happen.
Found the CSM was enabled, turned it off, after which never got video.  Tried two other video cards, still no video.
Cleared CMOS, board boots again, same error during install.  Was surprised to find after clearing CMOS that the CSM was enabled by default.
Turned off CSM, no video.
Is that a "feature"???  Doesn't seem like the CSM should affect video...
Is this something that would be fixed in a bios upgrade?

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playermikeb Members Profile Send Private Message Find Members Posts Add to Buddy List Newbie Joined: 05 Oct 2016 Location: usa Status: Offline Points: 6	Post Options Post Reply Quote playermikeb Report Post Thanks(0) Quote Reply Topic: 970m pro3 disable csm = no video Posted: 06 Oct 2016 at 1:21am
	installed this board in place of a bad one in oem machine. Reinstalling windows 8.1 x64, it says can't install to the disk bc it is of the gpt type. Well, this is an EUFI board and 64 bit windows, so that shouldn't happen. Found the CSM was enabled, turned it off, after which never got video. Tried two other video cards, still no video. Cleared CMOS, board boots again, same error during install. Was surprised to find after clearing CMOS that the CSM was enabled by default. Turned off CSM, no video. Is that a "feature"??? Doesn't seem like the CSM should affect video... Is this something that would be fixed in a bios upgrade?

Xaltar Members Profile Send Private Message Find Members Posts Add to Buddy List Moderator Group Joined: 16 May 2015 Location: Europe Status: Offline Points: 22703	Post Options Post Reply Quote Xaltar Report Post Thanks(0) Quote Reply Posted: 06 Oct 2016 at 1:33am
	My guess would be that the video card does not support UEFI (GOP). What GPU are you trying to use?


playermikeb Members Profile Send Private Message Find Members Posts Add to Buddy List Newbie Joined: 05 Oct 2016 Location: usa Status: Offline Points: 6	Post Options Post Reply Quote playermikeb Report Post Thanks(0) Quote Reply Posted: 06 Oct 2016 at 7:17am
	originally an nvidia gtx 460. Twice now, the video was fine, until i disabled the CSM. When i cleared CMOS, video resumed working.

playermikeb Members Profile Send Private Message Find Members Posts Add to Buddy List Newbie Joined: 05 Oct 2016 Location: usa Status: Offline Points: 6	Post Options Post Reply Quote playermikeb Report Post Thanks(0) Quote Reply Posted: 06 Oct 2016 at 11:08am
	whew, thought the board had croaked - had to leave CMOS battery out for over an hour to get video from ANY card again. Instead of outright disabling CSM, i disabled all 3 options under it. With an older video card, the board posts a warning that the VBIOS of your discrete vga card does not support UEFI GOP... With a new vid card (now a gtx 750ti), and using F11 to select UEFI DVD for boot dev, i can now select the partition on the hdd - the warning about it being the gpt type is gone. So perhaps the CSM being automatically enabled was a problem, or maybe i selected legacy DVD boot before? Whatever it was, i'm not touching anything until this <bleep>ing install is done.

parsec Members Profile Send Private Message Find Members Posts Add to Buddy List Moderator Group Joined: 04 May 2015 Location: USA Status: Offline Points: 4996	Post Options Post Reply Quote parsec Report Post Thanks(0) Quote Reply Posted: 06 Oct 2016 at 12:16pm
	CSM is Enabled by default. That is because older video cards do not support GOP, which is necessary when you "UEFI Boot", ie, set CSM to Disabled. Yes, UEFI/BIOS option defaults are dumbed down for the masses, more than you know. If you did not set CSM to Disabled, or set Launch Storage OpROM Policy to UEFI Only, then you Legacy booted. When CSM is Enabled, the UEFI firmware is run in emulated legacy/BIOS mode. CSM is Compatibility Support Module. The only feature of UEFI firmware normally used is the ability to use the GUI type interface. The entry in the Boot order will have, "UEFI:" as a prefix of the boot device name, if you have UEFI booting enabled. If you don't select that entry, you won't get a UEFI booting Windows installation. Your EVGA GTX 750 has a GOP compatible VBIOS out of the box, so it will work with CSM set to anything. A GTX 460 is incapable of being GOP compatible, it's VBIOS cannot be updated for GOP compatibility. So are all video cards of the same age or older than the 400 series. If you want to use the 460 in your board again, just put it in the board, and set CSM to Enabled. UEFI Windows installations include a hidden MBR partition, so work in both modes. That is, if it is done correctly. EVGA GTX 600 series video cards can be GOP compatible with the appropriate VBIOS update. That must be requested from EVGA, and applied by the owner. Any other video card manufactures, you'll need to check. Assume they are not GOP compatible until proven otherwise. EVGA 700 series cards and newer are all GOP compatible. Again, other manufactures, on a case by case basis, and it must be checked. I hope by now they would be, if not that is pathetic. Intel's integrated graphics have been GOP compatible since 2012.


playermikeb Members Profile Send Private Message Find Members Posts Add to Buddy List Newbie Joined: 05 Oct 2016 Location: usa Status: Offline Points: 6	Post Options Post Reply Quote playermikeb Report Post Thanks(0) Quote Reply Posted: 09 Oct 2016 at 9:29am
	Thank you for the detailed response. I don't believe i tried the 750ti when CSM was disabled, perhaps that is why turning off CSM caused complete loss of video. Just for fun, once win 8.1 was fully installed and working, i put the gtx 460 back in, the system booted without any problems or warnings. I have left the 3 items under the CSM section disabled, just bc i'm not changing ANYthing that might break the magnificent win 8.1.