Interesting Parsec glitch

[+mizapf]

I recently discovered a weird effect when testing the MAME emulation of Parsec, and at first I thought it was a bug in the emulation.

 

Some laser shots remained on the screen, as if the laser shot froze. When a star appeared on that line, it cleaned away the shot when wandering to the left. Since I could not remember such an effect, I first believed it was a regression, but I could not find an earlier release where it did not appear. Either the error was there for years, which was unlikely, or something has changed in the configuration.

 

The latter was the case: Some time I had a game that required Joystick 2 instead of 1, and I simply defined the directions and button of Joystick 2 to be the same as 1. Parsec checks both joysticks, so this meant that when I pressed the fire button, Parsec got button presses from both joystick 1 and 2. This obviously causes Parsec to "forget" the first shot of Joystick 1 after drawing it, and then do the fire action of Joystick 2.

 

If you have a real console with Parsec and two Joysticks, you may try the same and verify my theory. Play it with Joystick 1, and let a second person press the Joystick 2 button.

 

(And a rule for MAME configuration: Do not use the same input sources for both joysticks.)

 

[+adamantyr]

Oh yeah, this bug is in the software itself. My brother and I discovered it back in the 80's while playing Parsec. It had some other weird effects too; we started getting killer satellite's showing up before we hit level 4.

[Omega-TI]

1 hour ago, adamantyr said:

Oh yeah, this bug is in the software itself. My brother and I discovered it back in the 80's while playing Parsec. It had some other weird effects too; we started getting killer satellite's showing up before we hit level 4.

I seem to remember something about crashing your ship three times in succession at the beginning of a game, then continue playing and that would bring them out.  It's been so long ago that I'd have to try it all over again to confirm that.

[+mizapf]

I know that you should not move upward after the asteroid belt, or you may get a "wrap-around crash with ground" in some occasions, but not rare enough to be just ignored (lost quite some ships from that).

 

I also seem to remember that a velocity overflow may happen (I don't think that I just dreamt it).

 

Another challenge, but not a bug: Try to get behind the white ships (Urbites, Dramites, Bynites); then it will fire at a rapid rate when you are on the line (but behind them).

[sometimes99er]

http://xona.com/about/computers/ti994a/parsec.html

[+OLD CS1]

Yah, this a trick to help make the Dramites appear.