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Re: 16-bit real-mode code
- From: Etienne Lorrain <etienne_lorrain at yahoo dot fr>
- To: Josef Angermeier <sijoange at cip dot informatik dot uni-erlangen dot de>, gcc at gcc dot gnu dot org
- Date: Thu, 24 Feb 2005 07:30:52 +0100 (CET)
- Subject: Re: 16-bit real-mode code
> I ponder about writing a "i386 16bit realmode" gcc backend as my master
> thesis - which would be usefull for generating 16-bit bios code needed
> by the virtual machine developed at my university.
I do not know the virtual machine at your university, but there is
two different project you may have:
- writing a 16 bit realmode compiler (i.e. ia16 instruction set)
- writing a i386 in real mode compiler
If you plan to be able to use registers eax,ebx,ecx,edx... which exists
as standard in real/virtual mode on a i386, and also accept to use the
SIB32 addressing modes i.e. accept "mov $2,(%esp)" when the 16 upper bits
are null, then you would better directly use GCC to produce realmode
code, and see my bootloader based on that (http://gujin.sf.net).
If you also need to run on 80286 and lower processor, then you need
to rewrite the GCC backend and scan GCC archives to find the different
starting points available.
Etienne.
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