Date   : Sun, 09 Jun 2013 21:38:00 +0200
From   : eelco@... (Eelco Huininga)
Subject: 16-bit x86 assembler

Hi,

You can find an annotated disassembly of the 80186 copro BIOS at 
http://acorn.huininga.nl/pub/docs/sourcecode/Acorn/80186%202nd%20processor/80186.asm
Hope this helps.

Cheers,
Eelco


On 9-6-2013 14:22, J.G.Harston wrote:
> I'm recreating the source for the 80x86 CoPro client ROM[1]. I was
> using the 80x86 assembler in BBC BASIC for Windows, but as it's a 32-bit
> assembler it emits 32-bit opcodes to run in a 32-bit environment, for
> instance:
>
>      mov bx,&0033 gives 66 BB 33 00
>
> instead of what I require:
>
>      mov bx,&0033 gives BB 33 00
>
> changing register names to ebx, etc., gives the correct opcodes for
> register-to-register operations, but the above then gives the 32-bit
> sequence:
>
>      mov bx,&0033 gives BB 33 00 00 00
>
> The source is too big to load into DOS BBC BASIC which has a 16-bit
> assembler. Are there any 16-bit x86 assemblers that people could
> recommend, either to run on RISC OS or DOS/Windows? Ta.
>
> [1]http://mdfs.net/Software/Tube/80186/v100.src
>