Why would i3-3225 need CSM?

[wpcoe]

My motherboard has UEFI options to boot into SecureBoot and to boot into CSM mode. Those modes are mutually exclusive, it seems. If I enable SecureBoot, CSM cannot be enabled.

With SecureBoot enabled, I cannot boot into Windows. Usually I have to short the CMOS reset jumper to reset everything to defaults and start again.

I'm deducing that the i3-3225, and perhaps specifically its IGP, needs CSM. With CSM enabled the UEFI (BIOS) screens appear (mirrored) on both my monitors. With CSM disabled the UEFI screen only appears on one screen, hence my deduction.

I only have a general understanding of CSM, but my impression is that it is needed for devices that don't support UEFI booting. Why would a fairly modern CPU like the i3-3225 not fully support UEFI boot?

 

[sm625]

I think CSM is there to allow the UEFI to boot MBR type partitions. See here for more info: https://bbs.archlinux.org/viewtopic.php?id=142637

 

[wpcoe]

I thought CSM was for hardware that wasn't UEFI compatible?

I just disabled CSM, leaving SecureBoot also disabled, and I cannot get the Award BIOS logo screen (the one with "press Delete or F2 to enter setup"). Only a beep. If I press Delete right after the beep, I can enter UEFI setup. However with CSM disabled, only one monitor displays the image, and with CSM disabled I cannot boot into Windows.

Re-enable CSM (SecureBoot disabled) and I can enter UEFI with it displayed on both screens. I can also boot into Windows. WITH that ANNOYING "SecureBoot isn't configured correctly" watermark.

I also disconnected the 1TB HDD which is MBR formatted, so that the only drive is my UEFI SSD boot drive (the Samsung EVO).

There is some correlation between CSM and the video display, and since I have no discrete video card, that seems to indicate the Intel 4000 IGP.

The only hardware connected to the motherboard are the three drives and the CPU, the CPU fan and one case fan.

 

[ViRGE]

I thought CSM was for hardware that wasn't UEFI compatible?

That's correct. The Compatibility Support Module is the BIOS emulator for OSes that aren't designed to boot from UEFI.

I just disabled CSM, leaving SecureBoot also disabled, and I cannot get the Award BIOS logo screen (the one with "press Delete or F2 to enter setup"). Only a beep. If I press Delete right after the beep, I can enter UEFI setup. However with CSM disabled, only one monitor displays the image, and with CSM disabled I cannot boot into Windows.

That's completely normal. One of the features of UEFI is that it can boot very quickly, so it has a minimal initialization routine that offers little chance to punch in any keystrokes before passing on to the OS bootloader. Some mobos allow you to configure a specific interval for this; on others you'll have to tell the OS to reboot into the UEFI configuration program.

Re-enable CSM (SecureBoot disabled) and I can enter UEFI with it displayed on both screens.

Also perfectly normal. If you have one display adapter that's UEFI capable and one that is not, only the UEFI capable one will be used inside the UEFI configuration program.

As for your problem at hand, I'm going to wager you installed Windows in BIOS mode rather than UEFI mode. As such Windows isn't setup right to boot into UEFI mode, and if you try to force it, it will fail. Windows can only boot in the mode it was setup for. A UEFI setup needs UEFI to boot, and a BIOS setup needs BIOS (CSM) to boot.

 

[wpcoe]

That's correct. The Compatibility Support Module is the BIOS emulator for OSes that aren't designed to boot from UEFI.

Great. Glad to know I didn't get that part wrong!

That's completely normal. One of the features of UEFI is that it can boot very quickly, so it has a minimal initialization routine that offers little chance to punch in any keystrokes before passing on to the OS bootloader. Some mobos allow you to configure a specific interval for this; on others you'll have to tell the OS to reboot into the UEFI configuration program.

Quick Boot (or Fast Boot, or whatever it's called) is disabled. If I enable CSM, I see that screen for a few seconds before Windows boots. If I disable CSM, I don't see that screen. Just hear a single beep and the system hangs.

Also perfectly normal. If you have one display adapter that's UEFI capable and one that is not, only the UEFI capable one will be used inside the UEFI configuration program.

Is the Intel HD4000 IGP in the i3-3225 treated like two adapters to send the signal to two screens, and only half of that setup is UEFI capable? (I have no discrete graphics card.)

As for your problem at hand, I'm going to wager you installed Windows in BIOS mode rather than UEFI mode. As such Windows isn't setup right to boot into UEFI mode, and if you try to force it, it will fail. Windows can only boot in the mode it was setup for. A UEFI setup needs UEFI to boot, and a BIOS setup needs BIOS (CSM) to boot.

I installed Win8.1 from the UEFI device listed for the USB thumbdrive. The unpartitioned SSD was then GPT partitioned by the Win8.1 installer. Is there something missing from that process that would have installed in BIOS mode? Other than the disk showing in Disk Management as having a "100MB Healthy (EFI System Partition)" how can I be sure that Windows installed in UEFI mode?

Using EaseUS Partition Master, all partitions are shown as GPT:
- 300MB Recovery,
- 100MB EFI System Partition,
- 128MB Reserved Partition,
and then two Data Partitions.