Impossible Mission

[xZanU]

So the other night I was reading through all the threads in the 7800 hacks forum and came across a gem. It is the .a78 version (there is a bin too) of the fixed NTSC version of Impossible Mission.

 

http://pages.cs.wisc.edu/~harvey/7800/7800.html

 

I had been googling for it before, but never found it, however Mitch posted the above link in the thread.

 

This game is really very neat, you have a lot of stuff to do and play around with. If anyone never bothered with the game because of the bug that made it impossible to complete, the possible mission file on that website lets you complete the game (Fixes the bug). I know the PAL version works fine, but the NTSC does not.

[Atarifever]

I have the fixed version on cartridge. Fat lot of good it does me. I couldn't finish this game if they removed the robots, so that glitch would never have really effected me.

Edited February 21, 2009 by Atarifever

[xZanU]

I have the fixed version on cartridge. Fat lot of good it does me. I couldn't finish this game if they removed the robots, so that glitch would never have really effected me.

I just started playing it and thought it was fun. The Robots look great, the first group I encountered were not to bad, lots of timing to be done. I really like how the main character jumps. I was playing without looking at the manual so things were a bit confusing, but I will take a look at that soon.

[thursday83]

I have the fixed version on cartridge. Fat lot of good it does me. I couldn't finish this game if they removed the robots, so that glitch would never have really effected me.

I just started playing it and thought it was fun. The Robots look great, the first group I encountered were not to bad, lots of timing to be done. I really like how the main character jumps. I was playing without looking at the manual so things were a bit confusing, but I will take a look at that soon.

 

I agree with Atarifever, I also have a fixed version on cartridge, and I don't actually think I would ever know if it's actually fixed because I can never get far enough regardless due to the robots and whatever else....I try and try, for years now....And it's a fun and great game that gets lots of mileage, but I doubt I'll ever see the day that I can beat it. With the time factor, and the robots, and putting together the puzzle, ugh, I just can't seem to hack it at this game.

 

Another quick poke at the game: I just wish that they would have added the human voice of "Ahhhhhhhhhhhhhh" when he fell down the hole like the C64 version does, that is what made me love this game when I was a kid anyway, in addition to the front flip jump.

[Mayhem]

I've not tried the fixed NTSC version actually. I've complete the PAL version, but then again, I've played IM to death so it's all back of the hand to me

[Lord Thag]

I really need to get the patched version on cart. Always wanted to play through this game.

[+Propane13]

Ah, my old site is still there.

 

Glad you like the fix. It was a fun project.

 

-John

[xZanU]

Ah, my old site is still there.

 

Glad you like the fix. It was a fun project.

 

-John

Thanks for fixing! It is very much appreciated : )

[phuzzed]

i remember receiving this game for xmas one year, and I played and played it and searched everything and got all of the card keys that I could, but never could figure out how to finish the damn game. i got so darn frustrated with it... Only to find out years later that it really was impossible.

 

How in the hell did Atari let this slip through Quality control in the first place, is what I want to know.

[+Mitch]

The programmer for IM was on here a few months ago and he said he thought it might have crept in when Atari asked him to modify the game to run on 8K RAM instead of 16K RAM. If you search for the thread, you'll find a lot of other good info in there as well.

 

Mitch

[roadrunner]

I have the NTSC version of Impossible Mission. It's a fun game but those robots are a real pain.

My best total score is 1,000

[krewat]

Ah, my old site is still there.

 

Glad you like the fix. It was a fun project.

 

-John

 

John, what was the fix, do you remember?

 

 

i remember receiving this game for xmas one year, and I played and played it and searched everything and got all of the card keys that I could, but never could figure out how to finish the damn game. i got so darn frustrated with it... Only to find out years later that it really was impossible.

 

How in the hell did Atari let this slip through Quality control in the first place, is what I want to know.

 

No clue. I know they got a working copy, because I played it through to the end a few times before giving it to them. Then they tested it, signed off on it, and said it was good.

 

This was tested with the RAM development cartridge that I made myself, and I assumed at the time that they played it in EPROM, because they had come back with a bug in WG (I think) that was related to RAM vs. EPROM.

 

The programmer for IM was on here a few months ago and he said he thought it might have crept in when Atari asked him to modify the game to run on 8K RAM instead of 16K RAM. If you search for the thread, you'll find a lot of other good info in there as well.

 

That would be me.

 

I compared the last binaries I have for it to the "buggy" rom, and sure enough, they match. So, whatever happened, I supplied them with it.

 

However, if I remember correctly, as Mitch said, I believe I had to shrink the RAM footprint down and that is what introduced the bug. Again, if I remember correctly, as I originally supplied it, it wasn't much over 8K so it wasn't too hard to modify.

 

Funny thing about the running/jumping man graphics. Pretty hard to get to look right on the 7800, compared to the original C64 version I worked from.

[phuzzed]

krewat--

 

No harm done I still played the game to death trying to figure out how in the world to finish the game. I was pretty good at the game, and I remember on several occaisions, having searched everything that I could and sitting there trying to figure out how in the world to get the card key to go together!

 

Before I knew the game was really impossible, I remember looking at my brother and saying "Who in the world can finish this impossible thing? I don't think you can!"

 

If only I would have known....

 

But, thanks for sharing your stories about this. That is very interesting and I finally feel some closure

[+Propane13]

Ah, my old site is still there.

 

Glad you like the fix. It was a fun project.

 

-John

 

John, what was the fix, do you remember?

 

 

Here's the way I did it (which is going to sound totally crappy).

1) The PAL version works, so I did a diff of PAL vs NTSC.

2) There were a lot of diffs that were $00's compared to $FF's.

I attributed these to differing EPROM blank states (some start at $00, some start at $FF)

So, "nonprogrammed" spots I just ignored

3) I went through what was left, and found the items that were color changes and DLL changes.

The DLL's will be slightly longer in PAL, so those diffs were easy to find.

The color changes are easy too-- if there's a list that's like $66, $56, $76, and it suddenly now is $96, $A6, $26, it's likely a color table.

4) After identifying this data, I tool the PAL bin, changed any DLL numbers back to their NTSC versions, and took the NTSC colors.

Once that was completed, I burned a ROM, and it powered up, and surprisingly was finishable.

 

If you were looking to find the exact buggy code, I don't know how to solve that, but, there is good news.

If you diff my version vs the NTSC, version, the amount of diffs to start with is smaller than doing a full compare of PAL vs. NTSC.

That hopefully, would save you some time.

 

Hope that's useful info!

 

Regards,

-John

[xZanU]

Funny thing about the running/jumping man graphics. Pretty hard to get to look right on the 7800, compared to the original C64 version I worked from.

When I first played the game, I was really impressed on how smooth that jump looked, I actually said "Wow, neat!" when I jumped for the first time.

[krewat]

Here's the way I did it (which is going to sound totally crappy).

1) The PAL version works, so I did a diff of PAL vs NTSC.

2) There were a lot of diffs that were $00's compared to $FF's.

I attributed these to differing EPROM blank states (some start at $00, some start at $FF)

So, "nonprogrammed" spots I just ignored

3) I went through what was left, and found the items that were color changes and DLL changes.

The DLL's will be slightly longer in PAL, so those diffs were easy to find.

The color changes are easy too-- if there's a list that's like $66, $56, $76, and it suddenly now is $96, $A6, $26, it's likely a color table.

4) After identifying this data, I tool the PAL bin, changed any DLL numbers back to their NTSC versions, and took the NTSC colors.

Once that was completed, I burned a ROM, and it powered up, and surprisingly was finishable.

 

If you were looking to find the exact buggy code, I don't know how to solve that, but, there is good news.

If you diff my version vs the NTSC, version, the amount of diffs to start with is smaller than doing a full compare of PAL vs. NTSC.

That hopefully, would save you some time.

 

Hope that's useful info!

 

Actually, that's quite inventive.

 

I already did do a diff between the fixed version and my original, not that I saved it or anything, but it looked like someone at Atari hacked the crap out of it.

 

In other words, there were NOPs thrown in to fill in the holes. Obviously someone worked on the binary, and not the source. It probably would be near impossible (pun intended) to recompile the thing from what I gave them. Actually, I'm not entirely sure Atari ever got the source code from me.

 

Maybe one day real soon I can revisit this and put the issue to bed as to what I screwed up

 

--

 

As for the graphics, I really don't remember if I personally did the graphics for the running/jumping, but I seem to think I did. I remember long hours in PCPAINT trying pixel placement to make the figure look decent on a TV. Which was actually quite fun. You could look at it on a PC monitor and it was obviously horrible looking. (not to mention the colors on my CGA PC/XT monitor were only three - magenta/cyan/white) But throw it through my converter, and then the double TV analog conversion (to NTSC video, and then to channel 3) and it suddenly looked all nice and shaded at a resolution that was totally impossible. (no pun intended) Of course, I might be out of my mind and I'm thinking of another 7800 game I worked on.

 

Here's the graphics for the man, from the original .PIC file I have:

[xZanU]

Here's the graphics for the man, from the original .PIC file I have:

He is so tiny! Thanks for that, fun to see all the steps involved for the animation.

[krewat]

By the way, I didn't author the graphics from scratch, definitely used what was there from the C64 version. But again, not too many colors to work with compared to the C64.