rdos wrote:
Yes, because this is information that VBE will provide for you. So, you don't need GRUB, only VBE.
...Except on UEFI, where GRUB will work exactly the same way as it does on BIOS, and VBE will not.
davmac314 wrote:
The BIOSes came first, though. I suspect the reason that BIOSes mostly work in v86 mode is because v86 mode is, in fact, largely compatible with real mode which the BIOS "natively" supports and for typical BIOS operations there's no reason to do anything funky enough that would show up an incompatibility between real mode and v86 mode.
ISA option ROMs need to maintain backwards compatibility with a 286 (or sometimes 8088), which prevents the use of any funky tricks that wouldn't work in v86 mode. VGA option ROMs completely replace the original BIOS INT 0x10 handler. Microsoft could safely assume the INT 0x10 handler would run in v86 mode, and as Windows took over the PC ecosystem, Microsoft effectively forced later option ROMs to maintain v86 compatibility.
It's perfectly reasonable for a VGA option ROM to switch to protected mode in order to access its MMIO, yet you'll find very few that do so.