[Wiltshire] Wine, Dosbox, ScummVM

[Andrew Meredith]

On 11/01/11 21:09, Sharon wrote:
> Hi all,
> 
> A slightly different subject.  I have resurrected my old windows game
> that I am rather fond of.  Some I play under Dosbox, some under Wine and
> others work in ScummVM.  My favourite is a really old game named 'The
> seventh Guest'.  Though I can get the game to run under Dosbox it
> usually crashes at some point but under ScummVM it works superbly. 
> These games are all old  dating back to Win95/Win98 and are exe files. 
> What is it that makes them work in the different formats.  Why does 7th
> Guest work both in ScummVM and Dosbox but Micemen only works under
> Dosbox and Sherlock which is of the same era works under Wine.  I can't
> figure what differentiates them all.  But one thing ... these good old
> windows games are all working on Ubuntu.  Pretty neat.
> 
> Only curious ...
> 
> Thanks for any info.

As I understand it from coding in Windows to deliberately run under an
emulator a while back; it's all down to the API calls used when it was
written. For a long time there was a proper published API for any given
version, but a whole pile of undocumented ones that got the job done
quicker. These undocumented ones sometimes got documented and others got
changed a little bit and then fixed and others dropped. The practical
effect is that if you try running a binary built for using one layout
and run it in an emulator of another layout, the "clean" code will run
fine, but the first time it calls the now slightly squiffy connection to
the back door API call, it goes boom. Oh and before you start wondering
why people would use these calls, the answer in a lot of cases was quite
simple; if you didn't use them you would either have to use a massively
slower call or indeed couldn't do the thing at all. Back in the day, I
had to use some for graphics work that would be unshippably slowed down
if the formal call was made. Bet that code would blow up most
convincingly under pretty much any emulator :)

Andy M

-- 
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         Andrew Meredith BEng CEng CITP MBCS MIET
	 http://www.anvil.org    andrew at anvil.org
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