Re: [stella] SoftVCS

Subject: Re: [stella] SoftVCS
From: "C. Bond" <cbond@xxxxxxxxxxxxx>
Date: Tue, 30 Sep 2003 12:39:47 -0700
Fabrizio Zavagli wrote:

> Hi!
> C. Bond wrote:
> > I just posted some preliminary applications using a new Atari 2600
> > emulator called SoftVCS.
> I've just been able to try your softVCS player and analyzer, and definitely
> appreciated the moves being done torwards a debugging tool!
> Now I know that it's and Alpha release, but since you made it public, I
> believe you're expecting some comments so here we go!
> First of all, just for information, the emulator itself is not running full
> speed on my system (a 1.4ghz AMD), but I guess I've been warned :)
> Anyway, I was surprised that the "player" came without a "load rom" option,
> but instead could only play a set number of roms (supplied with the exe!).
> Has it been done because of compatibility (the roms supplied are the ones
> that work best), or maybe you would like to create a menu with screenshots
> for all the known VCS games?
> Now, obviously the Analyzer is the tool that got most of my attention. Are
> you planning on further improving its debugging capabilities?
> Regards,
> Fabrizio.-

Hi Fabrizio,

Thanks for taking the time to try the game player. This application is simply intended to
demonstrate a proof-of-concept with a very limited implementation of the emulator engine. When I
add bankswitching and full input capability, I'll post another application supporting the "load
ROM" option.

As I mentioned, allowing the user to resize and reshape the game window in a Windows version
independent manner means working with the GDI, and the overhead is ridiculously high. The engine
itself should only use about 3msec per frame on your system, and Windows hogs the rest. This is
unfortunate, but I wanted an 'interactive' screen capability so the Analyzer and future debuggers
can select any pixel to analyze. Processors continue to get faster and I can probably get
improvements in the engine when I get most of the bugs out, so there's nowhere to go but up!

As far as a debugger goes, I have already included an instruction trace buffer and a hit counter
for each opcode so I can add the ability to trap on any line or pixel and dump the instruction
history, zero page, processor registers, timer values, etc. during actual play. I can't give an
estimate about how long this will take because I want to make progress at debugging the core code

For the record, I have the following emulator problems:

1) Some games to not play at all, (Chopper Command),
2) Some are too far garbled to play, (Adventures of Tron, Cosmic Ark),
3) Some exhibit vertical jitter, (Frogger),
4) Several have incomplete score displays (Pitfall).

I know most of the problems are due to timing errors, but I haven't gotten them under control yet.

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