Toshiba Satellite S55-B5280 With Windows 8.1 Boot from CD

In the best of all worlds, I'd like to be able to boot this computer from CD.
This computer doesn't have a CD drive so I have to use an external USB DVD drive.  OK.
I have turned off Secure Boot.
Now it allows one to select an "EFI USB Device".  This does nothing with a typical live CD.
One CD would be a hard drive test live CD.
Lacking any such live-CD-based HD test capability then how might I test the hard drive - still in the computer?

Related:  If I turn off the EFI boot mode then will one still be able to boot from the Windows 8.1 hard drive?  Or, will that be lost?
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Fred MarshallPrincipalAsked:
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If you change from UEFI to conventional BIOS, you should be able to boot from normal CD's/DVD's. Just change it back to UEFI once you are done and want to boot the PC normally..

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Fred MarshallPrincipalAuthor Commented:
So, I need to make the computer *unbootable* from its normal hard drive OS.  Is that right?
And, the ability to both reach the controls to change it back will still be there, right?
And, once switched back, it will boot from the GPT drive once more, right?

This isn't my computer and I don't want to break it!!
You don't break a PC by changing BIOS settings, you just need to change them back when you are finished.
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Fred MarshallPrincipalAuthor Commented:
I've been pursuing an alternate approach as well: Boot from USB that works with EFI.  But I'm having trouble making it work on this Toshiba.  I can build USB flash drives using Sardu, which is somehow supposed to work with EFI using some version of Grub but the Toshiba doesn't respond to them.  Older computers do.
Fred MarshallPrincipalAuthor Commented:
I've learned a bit:  One cannot expect to convert an .iso that boots pre-UEFI to a file/device that boots under UEFI.  Part of this has to do with the file contents being insufficient.  So, while one may be able to build a UEFI bootable USB drive, it can't be done with just any .iso.

So, first of all, the computer needs to be set with Secure Boot not enabled.
Then, the computer needs to be set to boot from various devices.
Then, the device needs to contain a file that's bootable under UEFI or EFI.... which may be a bit elusive.
Otherwise, the boot needs to be changed from UEFI to CSM.  
It depends on the OS you are booting. For example in order to boot from USB stick that is used to install Windows from, it must be formatted with fat32 so you can install it in EFI mode to a GPT disk. If that is the case, when you boot from the stick and the BIOS is set to UEFI, you should see the stick twice, once as a UEFI stick, and once as a normal stick, and then you can select which one to boot from. If it was formatted in NTFS you will only see it as normal stick, without UEFI, and you will only be able to install the OS in Legacy mode to an MBR disk.
Fred MarshallPrincipalAuthor Commented:
Yes, there is much written about such things to install Windows.
What I was focusing on were the more generic .iso images for testing HDs, AV, cloning, etc.
you could also use an external cd drive -  they are cheap :
For linux based iso's, it depends on the distro. many support both, UEFI and conventional BIOS, while some only support conventional BIOS. for things like the UBCD only conventional BIOS.
Fred MarshallPrincipalAuthor Commented:
At the moment I'm focused on tools and not OS installations.  Just to be clear.
The tools are on live CDs that are based on one OS or another.  So, no real "distro" involved - just the choice of the tool builder.  So yes things like UBCD.

I don't see how an external cd drive effects the discussion.  In fact, that's what we're using in one of the first attempts at doing this.

It may be of interest and/or you may have comment:

We were working today on a Lenovo X240 laptop that originally came with Windows 8.x and has been upgraded to Windows 10.  It is a UEFI machine.  It has no DVD drive.
Secure Boot is off.
UEFI / not CSM is selected.
From Windows, we wrote a System Image file onto an external USB HD.
We built a Recovery CD at the end of the imaging process as suggested in Windows - using an external USB DVD drive.
We then attempted to boot from that same CD in order to write back the System Image.
The system would not recognize the CD that had just been written.

So, from THIS thread, might I assume that the procedure for recovery of the image would be:
- switch from UEFI to CSM.
- boot from the CD
- write the image onto the internal HD
- switch from CSM to UEFI
Fred, it seems i misread your question, sorry for that
i would test first if you can boot from a known good bootable cd - as i answered in your other question about this problem
Fred MarshallPrincipalAuthor Commented:
nobus:  Sure.   But still in CSM mode, right?
what is CSM mode ?
Fred MarshallPrincipalAuthor Commented:
CSM = Legacy BIOS boot mode if you like.
i know bios mode - just wondering what CSM means; maybe cmos mode?
i must say the systems i've seen work as well in both modes - when safe boot is turned off in the uefi mode
Fred MarshallPrincipalAuthor Commented:
CSM=Compatibility Support Module providing legacy BIOS compatibility.
I tend to avoid saying "BIOS" when possible because the UEFI is also a BIOS in some sense.  They are both firmware but written to different standards.  In that sense, they provide the same type of function but with different capabilities, features, etc.
i agree there is often confusion in the terms cmos - bios - uefi
tx for the info -  another one to remember
Fred MarshallPrincipalAuthor Commented:
It looks like we all learned something.  Thanks!
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