Re: Fw: 16-bit bootloader support?

[Bogdan <love4boobies@yahoo.com>]

Again, sorry for the top-down mail. There will be a patch just as soon as I get a bit of spare time (this weekend might be a good opportunity). All I have now is a hack that will work for my system under well-known conditions.

Cheers,
Bogdan


----- Original Message ----
From: Robert Millan <rmh@aybabtu.com>
To: The development of GRUB 2 <grub-devel@gnu.org>
Sent: Fri, October 9, 2009 8:55:02 PM
Subject: Re: Fw: 16-bit bootloader support?

On Fri, Oct 09, 2009 at 02:21:06AM +0200, Vladimir 'phcoder' Serbinenko wrote:
> Bogdan wrote:
> > The difference is basically that you have no paging, the linear address is the same as the physical address, no virtual 8086 mode, no way of going back to real mode, the segment address inside the descriptor table is 24 bits wide and the limit is 16 bits wide.
> >
> > In response to Seth - there are still business and apparently research machines out there that still use the 80286. It's arguable whether one would actually need to be able to boot several OSes on such machines 
> For multi-OS on pre-386 use mbrldr (mbrldr.sf.net)
> > but I am an example of someone who is personally interested in this. If I write support for this can it be merged into GRUB 
> Rule of a thumb is "if you do it in a way it doesn't create a
> maintenance burden then it can be merged". Due to limited usefullness
> the amount of maintenance burden I'm ok to tolerate is small. I would
> define 286 as a separate architecture with perhaps some BIOS-related and
> realmode code reusage. This way it minimises the amount of it getting in
> the way
> Due to 16-bit pointers it's still likely to get in the way of a lot of
> code. Also even before you start you have to ensure grub2 can work with
> less than 1 MiB of memory.
> In whole I would say that maintaining 16-bit compatible code is a burden
> and probably not worth if only PC 286 is considered. Additionally
> without being able to load any kernel natively grub's usefulness
> decreases. Many other modules become useless too because newer standards
> aren't supported on 286 hardware. In whole I feel like multi-OS on 286
> and 8086 niche is well filled by mbrldr.
> (but I'm not maintainer)

I have very limited interest in this.  But if there's real demand (i.e. not
just a toy) and it doesn't mean more work for us, we could accept it.

Is there a proof-of-concept patch?

-- 
Robert Millan

  The DRM opt-in fallacy: "Your data belongs to us. We will decide when (and
  how) you may access your data; but nobody's threatening your freedom: we
  still allow you to remove your data and not access it at all."


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