28 replies to this topic

[Tripredacus]

OK I do not think it is a bug. For a board firmware (or BIOS) everything is really the same but the different companies use different wordings or settings in their menus. The system will choose to boot something first. We can see this on Asus boards. In CSM settings their boot control will say something like "UEFI first." So it would seem to me that a board set like that could boot a legacy USB key if no EFI ability were present. But if it is present, it will boot in EFI. If you were to set it for Legacy only and had a USB that could do either, it should be able to boot in Legacy mode right?

Also another reason why I wouldn't want to say it is a bug. Do we know exactly how a given firmware goes about its process? In the case of the Asus boards if set to UEFI first, does it:
1. Look for UEFI bootable devices first, and if found, boot them as according to the boot order set?
2. Try to boot the first device according to boot order in UEFI mode blindly, and then boot it in Legacy mode if it fails?
3. Look at all devices and then determine what boot methods they have and then process them as per the settings?

I had to put #2 in there because I can see this type of shortcut being made.

[steve6375]

A UEFI BIOS can either be set to UEFI-only or UEFI+CSM.

1. When it is set to UEFI-only, it will obviously only boot to UEFI.
2. When it is set to UEFI+CSM, some BIOSes will not boot in CSM mode if a UEFI boot file exists on the same device.

So, in either case, you cannot boot in CSM mode when you may wish to, AFAIK there was no 'boot Legacy first' setting in these BIOSes or any other setting which would allow it to CSm boot.

 

Unfortunately, I don't have one of these systems to test, but it is my understanding that there is not any BIOS setting will allow it to boot in CSM mode from the E2B USB drive if it also contains a valid UEFI boot file. Several people reported this issue on reboot.pro, but I cannot find the posts/thread...

 

P.S. This 'bug' materialised when I added the MemTest86 UEFI boot files to Easy2Boot so that if you UEFI-booted, you could run a memory test. Several people who made a FAT32 E2B USB drive, reported that they could no longer boot to E2B on their system and that there was no way they could make it boot. When they deleted the .EFI files, it could then boot to grub4dos and the E2B menu.

Edited by steve6375, 28 September 2016 - 10:11 PM.

[Tripredacus]

A UEFI BIOS can either be set to UEFI-only or UEFI+CSM.

• 
  
• When it is set to UEFI-only, it will obviously only boot to UEFI.
• When it is set to UEFI+CSM, some BIOSes will not boot in CSM mode if a UEFI boot file exists on the same device.

But this isn't true. You have Intel NUC system that can be set to
- UEFI only
- Legacy only (it does not use the term CSM)
- UEFI+Legacy

Since all BIOS are different, even same providers but different ODMs (Barely any follow standards for UEFI and/or BIOS in general) you cannot make a blanket statement like that. You can put in dislcaimer that certain USB builds may not boot on all hardware configurations.

Link to me how I can make one of these memtest (or whatever) drives so I can test for you if you want.

[steve6375]

You can make a normal CSM-bootable grub4dos FAT32 USB drive - e.g. E2B using a FAT32 partition.

Then download and add MemTest86 http://www.memtest86.com/

Just copy the whole \EFI folder to the root of the USB drive.

 

You should then be able to boot via UEFI to Memtest86 or CSM boot to E2B/grub4dos.

 

Apparently, some systems (I think Fujitsu LifeBook was one) will not CSM boot to such a drive.