Can't access BIOS

Jack Cook7 said:There are just so many different versions out there.

Essentially, MBR doesn't really mean anything other than the actual content—that little bit of assembly code—located on the very first sector of the hard drive, which is where the IBM BIOS hands over control right after the POST process finishes. It basically just loads that first sector (which is 512 bytes, without any ECC) into a specific part of the RAM, and I guess the final instruction during the POST is just a jump to the very first instruction of whatever was just loaded.

Things have become a little more complicated over the last 40 years, thanks to Bill Gates, IBM, and Intel. To really explain the whole thing properly, I suppose I would need about two or three pages of dense, heavy text. I did touch upon a portion of this in that other thread regarding booting via a network card (PXE).

If I were to offer some advice, I’d suggest that the user should probably start by checking which USB port versions are available on both the source and destination machines, along with what USB version the flash drive itself uses. Most PCs and laptops nowadays seem to have a mix of both 2.0 and 3.0 ports.
Then we can actually get somewhere.

Also, EFI isn't quite the same thing as UEFI. UEFI supports MBR, FAT16, FAT32, and even MFT, but as I mentioned, things just get much more complex from there.

But honestly, none of that really matters. Either the motherboard supports the specific standard required by Windows 10 or it simply doesn't. If it does, then there shouldn't be a problem, but if it doesn't, then Windows 10 just won't work.

The tool will always create the exact same thing regardless of which computer you are using. Or, it won't create anything at all.

Besides, it seems to me like he is using the exact same machine for both the source and the destination, especially since he was trying to tweak Fast Boot within Windows and editing the registry, so I guess all of those technicalities are irrelevant here. We could certainly go down a rabbit hole of getting overly complicated, but since there's no real desire for that, I think we should just stick to the basics. 😬

That’s exactly what I’m getting at. We could sit here all day doing a deep dive into forty years of boot sequences—I mean, we could go way back to when you were manually toggling switches on a front panel just to program the bits, though I’ll spare us the lecture since I haven't actually rolled up my sleeves for that specific era myself! But honestly? We’re basically flying blind because the client's description is so vague. All we can really gather is that they’ve spent some time building boot environments for a massive variety of hardware, but that’s about it.

And don't even get me started on Secure Boot and how Microsoft uses their own logic to basically lock out the competition.

Jack Cook7 said:Things have gotten messy over the last 40 years, thanks to Bill Gates, IBM, and Intel. To really break this down, I’d need a solid three pages of dense text. I touched on part of this in the thread about booting via network cards (PXE).

My advice? First, check the USB port versions on both the source and destination machines, then check what version of USB the stick itself is. Most PCs and laptops have a mix of 2.0 and 3.0.
Then we can go from there.

Also, EFI isn't the same thing as UEFI. UEFI supports MBR, FAT16, FAT32, and MFT, but like I said, things get complicated.

It’s true you need pages of text😁, but here’s a starting point:

UEFI and BIOS are low-level software that run when you power on a computer, but UEFI is the modern version. It supports larger drives and stuff—that has nothing to do with FAT16 or FAT32.
New computers come with UEFI, but they just call it BIOS so they don't confuse people who actually know what BIOS is.

Basically, BIOS looks for the MBR sector, reads it, and kicks off the bootloader.
Old BIOS can't recognize HDDs larger than 2TB, so a new 3TB drive won't work.
There's also BIOS emulation on newer computers, but I don't think that needs explaining.
And obviously, UEFI uses GPT instead of MBR to dodge those old BIOS limitations.

There. Hopefully, we've helped the user stop obsessing over USB 2.0 vs 3.0 ports and start looking for the actual reasons for the incompatibility.

The BIOS isn't actually hunting for an MBR. It just grabs whatever is sitting on sector 1 based on how the disk controller presents it. I’ve been booting drives larger than 2TB for ages without even touching UEFI, though honestly, I ran into some massive headaches with anything over 2GB back in the day—even when the PC's BIOS and the OS were totally fine with much bigger capacities.

And then there's the whole saga involving those ST506 and ST412 interfaces. I’m pretty sure you guys know exactly why they matter so much for getting UEFI (or PXE) up and running.

Alright, let's start with the basics here.
1. Is the user making this bootable USB for their own rig or for a different machine entirely?