Emulator Bugs

From: lti@earthlink.net
Newsgroups: rec.games.video.classic
Subject: Re: Activision's 2600 Windows
Date: 23 Mar 1995 07:20:00 GMT
Organization: LTI
Lines: 35
Message-ID: <3kr7f0$5hf@mars.earthlink.net>
References: <matthewpD5uH7H.IEr@netcom.com>
NNTP-Posting-Host: lti.earthlink.net
X-Newsreader: AIR News 3.X (SPRY, Inc.)

>   matthewp@netcom.com (Matt Pritchard) writes:
>  
>  Alas, The emulator is not complete yet... It doesn't even run Adventure
>  100% correctly.  A Rather basic player control register isn't emulated
>  completely.  I spoke with the Author and he indicated that that it is
>  complete enough to run the carts in the current action pack and the
>  planned action pack, and that's all.  Give how many 'undocumented' tricks
>  were discovered/invented making 2600 games, a game by game tweaking of the
>  emulator is required to get 100% emulation. 
>  
>  

Greetings from the author:

I must say, I'm impressed at the speed in which you folks have been
able to hack the Pack!  Is nothing sacred! :)

Anyway, the emulator DOES actually emulate the play control register
and the graphics flipping.  The areas where things can get shaky is on
games that do strange stuff like write to the TIA via the stack, which
causes me to do extra checking every time a stack operation occurs and
makes for slower emulations.  I disabled this feature and three or
four games (like Demon Attack) had trouble.  I made the decision to
remove the stack I/O games from the first list and have since made
more speed improvements that should cover the extra cycles consumed by
those games.

The other area the the emulator may have trouble with is games that do
multiple mid-line things (ie:  horizontal multiplexing).  The emulator
will do this kind of stuff in most cases, but not all.  For example,
the emulator does support mid line collision checking and resets,
which games like Freeway do all over the place.  I have to say that
that feature was one of the major programming bitches I had to deal
with.

Best Regards,

Mike.

Michael Livesay
Livesay Technologies Inc
lti@earthlink.net