nullplan wrote:
At the moment, I'm using the CHS values as cookies; essentially nonsense values I just pass through to the BIOS.
There's no guarantee those values will make sense to the BIOS. If you must support CHS,
ask the BIOS what geometry it's using and translate LBA to CHS.
nullplan wrote:
DS:SI is supposed to point to the partition table entry when the VBR is jumped to, but that entry is useless if it is an extended entry, because the starting LBA is relative to the starting LBA of the partition table, which the VBR is never told.
Common OSes don't care about DS:SI and will boot perfectly fine without it, even the ones that refuse to install onto an extended partition.
nullplan wrote:
The only people that would get any utility out of an MBR that runs on a pure CHS machine are people running old hardware, and they have more than enough offerings already to do precisely that.
...Or would rather write our own.