>https://thestarman.pcministry.com/asm/mbr/mystery.htm
>but one of our readers finally pointed out that Microsoft did provide a "partial description of the meaning [of these bytes] in KB article 192606 (or the file: MBtFAQ)."
JFYI, I am this reader
And I know slightly more, of course - the real IOS structure that used for passing these values (signatures and checksums).
>Can you detail which cases?
Excerpt from your link:
>or the first word after the boot code is non-zero, IOS will instead store a checksum of the MBR and the INT 13h unit number, rather than the MBR signature.
And as checksum include NT Disk Signature too -> we have unique value of this checksum.
>But during setup?
I don't see how this can affect setup too (as you), but NT Disk Signature has some impact on Windows 9x.
P.S. And what it looks like in reality (with MBR code from NT):
int13 = 80h, signature = E6FFB000h, checksum = F601BDECh, flags = 0001h
int13 = 81h, signature = E6FFB000h, checksum = BDE79504h, flags = 0001h
int13 = 82h, signature = E6FFB000h, checksum = E6233B84h, flags = 0001h
Win9x signatures are equal, but checksums are different (and IOS is using checksums (flags = 0001h))