linux-os (Dick Johnson) wrote:
Who is YOU??? I would certainly be requesting the right sectors
if I (or anybody else who knows what they are doing), wrote
the boot code. The boot loader knows about OFFSETS into the
device where it's going to get its data, which eventually
becomes a whole operating system. It doesn't give a *uck about
anything else. There is a table of OFFSETS, obtained from
the file-system, of the correct pieces of files (since there
will not be a file-system until the machine is booted). This
table of offsets needs to be read somewhere in the first 63
sectors (32256 bytes). These offsets contain the junk to
be loaded into memory.
We weren't talking about a boot loader you would write, or lilo even, we
were talking about windows's boot loader, which, to the best of my
knowledge, directly passes the CHS address of the starting sector of the
partition stored in the MBR to int 13. That CHS address is calculated
by fdisk based on the geometry it believes the disk has and is written
to the MBR when you partition the disk. The last time I checked a dos
MBR, the boot code there didn't recompute the CHS address at runtime
based on the LBA and current geometry according to the bios, so it has
to be written correctly in the first place by fdisk, which requires that
fdisk know the bios geometry.
The boot-code, the code that executes in the 16-bit environment,
converts those offsets (after getting data from the DPB) into
the respective junk to put into the registers as I explained
over and over and over again.
Maybe I'm just dense, but that's not what I heard you explaining. Is it
your position then, that the MS DOS/WIN MBR does actually recompute the
CHS address at boot time based on the geometry the bios currently
reports, and the LBA in the partition table, rather than use the CHS
address stored in the partition table and precomputed by fdisk?
If that is the case, then fdisk can use whatever geometry it chooses and
everything will be fine, so why does the kernel have to carry around
some geometry instead of just letting fdisk make one up when it is run?
You refuse to learn. Please go away.
That is uncalled for. I don't understand why you have shown a bad
attitude this whole time.
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