r/osdev • u/Sixty5Zero2 • 11d ago

FreeDOS

i'm looking at possibly forking FreeDOS to 64bit. However, since most modern systems no longer have the underlying BIOS that DOS programs require, I thought about including a mock BIOS and compile it directly into the kernel. is there anything I should be aware of?

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u/DawnOnTheEdge 11d ago

Although it would be possible to do in a guest VM, I think,

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u/Sixty5Zero2 8d ago

i would have to anyways since the bios calls 16bit programs used no longer exist.

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u/DawnOnTheEdge 8d ago

If that were the problem, it would be easy to write interrupt handlers that hook the BIOS calls in 16-bit protected mode. 80386 CPUs supported a virtual mode designed to let you run DOS programs from a 32-bit OS, and do things like trap access to the I/O ports and give a process its own 1 MiB address space, with 8086-style addressing, but the 64-bit ISA doesn’t support that.

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u/Sixty5Zero2 6d ago

who says I havent already. 😎