Stella b/w bug

[Keatah]

Canyon Bomber's "depth-charge" line doesn't switch to B/W in accordance with the color/bw toggle.

[Rybags]

Probably not an emulator bug... run the game in the browser from Atarimania and you get colour appearing when B&W is selected.

 

B&W is just a port bit that the game can read and do anything it wants with, doesn't actually cause the system to disable colour.

Edited March 13, 2014 by Rybags

[+stephena]

Can you post the ROM? I tried with both 'Canyon Bomber' ROMs I have, and B/W worked fine. BTW, Rybags is correct in that the switch can be completely ignored by a game. But this one should be using it, and indeed it does in all my testing.

[Rybags]

It does recognise it, but even in attract mode with the colour cycling you'll notice occasional coloured areas.

The game type seems to make a difference as well, particularly the water based ones.

 

But I was able to replicate colour appearing in the Java-based emu on Atarimania which would seem to indicate the game itself is probably doing it.

[Nukey Shay]

Address $F1BF performs EOR #$40 just before updating PF color to draw the line...the game will display color for that line regardless of what position the switch is in. So it's being emulated correctly. What's missing in the program is an AND $E7 - this address holds #$FF when color, #$0F when B&W (i.e. color hues stripped), and bit3 stripped when attract mode is active in either case. Perhaps the programmer what short 2 bytes, didn't notice the problem, or didn't think it was of much consequence? The line is visible on a B&W television, so that is all that matters.

[+FujiSkunk]

Generally, for any game that does what you think it shouldn't with the B&W switch, it's going to be a "fault" of the game, not the hardware or an emulator. It's just a toggle, and it is completely up to the software to decide what to do with that toggle. That's why most games from 1982 onward don't even acknowledge the switch, and others use it for different functionality like pausing.

 

I remember back in the day noticing Canyon Bomber's target line was still in color with the switch set to B&W on a real 2600. As Rybags mentioned, some games also include color hues in their demo mode's color cycle, even with the switch set to B&W. The Empire Strikes Back is one such game.

[Nukey Shay]

Nevermind...stripping the color hue for the depth line would render it invisible in part of the screen (since the background color is graded for the "sea"). So the program is taking a correct approach to display it regardless of which mode it's in.