little bug in Yoomp (1.1) on Atari XEGS?

[Marius]

Hi!

 

Today I hooked up my Atari XEGS... just for fun. I only wanted to play games... and what is a better choice than this great XEGS.

 

My plan was: just play games from my SIC! Cart that do not need a keyboard.

 

So I fired up my SIC! Cart and played a few games on my XEGS (Millipede, Animal Party)... and then I wanted to play Yoomp!

 

That did not work!

 

On my Atari 800XL it works fine from the SIC! Cart but on the XEGS it does not get in the Welcome screen.

I thought: hmmm this is strange.

 

So I connected my XEGS-Keyboard, pressed reset, and there it was. Yoomp welcome screen.

 

Without the keyboard connected it does not work.

 

Anyone ever noticed this bug?

I hope it can be fixed in the future... I am going to use my XEGS a lot more now without the keyboard. It is a very nice machine!

 

Greetz

M.

[miker]

Maybe try booting XEGS without keyboard and with SELECT pressed. IIRC that key works in the opposite way when keyboard is not present.

 

I assume that you have original ROM there (with Missile Commnad game in),

[Marius]

Unfortunately it does not do the trick. I also tried that. When I look carefull i see the welcome screen of yoomp for 0.5 second, and then it goes to the "Start Level 1" screen with the music. But when I press fire nothing happens (the game hangs stuck, except for the music).

 

Switching on with Select pressed did not help.

 

Yes it is the original XEGS with Missile Command built in...

[Marius]

I might have found the possible issue.

 

When no keyboard is attached TRIG(2) ($D012) reads zero. Perhaps there is a slight possibility yoomp checks on any TRIGGER whether it is pressed or not.

 

As soon I disconnect my keyboard $D012 reads ZERO. This is the same as pressing a firebutton on a joystickport 3 on Atari 800.

 

TRIG(2) is hardware register. STRIG(2) (shadow) appears not to change. That is odd, I know.

 

But I'm pretty sure this is the issue.

 

I already contacted ERU. Perhaps he can fix this.

 

I found the same problem when I played BASKETBALL on my XEGS. The computer player is not able to play any ball. The ball moves all over the screen. That is a feature in the original ATARI 800 game, where different players can pass the ball to each other by pressing the fire button.

So as soon as no keyboard is attached on an Atari XEGS, the 'TRIG(2)' flag reads zero, which results in little compatibility issues when a game is using TRIG(2).

 

Interesting isn't it?!

 

Greetz

M.

[Marius]

Oh and another thing...

 

When you boot with no cart insert $d013 reads also ZERO!

 

So TRIG(2) and TRIG(3) are used to detect keyboard and cartridge on XEGS.

 

Well... that is what I think.

[Rybags]

Trig3 was reassigned as cart detect with the XLs.

 

Trig2 for keyboard detect is unique to XEGS.

 

The shadows don't reflect these states because the OS only shadows ports 1/2 and copies paddle/stick stuff to the other shadows.

 

 

Re the game - I suspect Yoomp ditches the OS totally once the game has loaded. Maybe it's not handling PORTB properly and inadvertantly switching the Missile Command ROM in or something.

Doing that would most likely make the game crash or not behave properly.

Edited November 30, 2011 by Rybags

[eru]

Yoomp! only uses TRIG0, but also uses SKSTAT ($d20f) for SHIFT detection.

 

Since the game starts immediately, it would suggest either of these pressed. Or START press is detected, but I doubt CONSOL ($d01f) is influenced on XEGS.

 

No idea.