Kurt_Woloch

About Pitfall II: Out of curiousity, I tried the SG-1000 version of that (in fact, I fully mapped it out), and while it resembles the arcade version, it also has got some notable differences: 1. There's no time limit like in the arcade (and, I think, all the others) 2. You can (relatively) freely move around in the map. In contrast to that, in the arcade version the maze, while being a consistent "whole", is divided up in "levels", that is, reaching a certain point marks the end of one "level", which lets you start at a slightly different point. In the SG-1000, there's no such divisions... you just play through it and basically are able to return to any point in the maze 3. It wraps around... unlike both the arcade and CV versions. Which means, if you go right from the rightmost screen, you arrive at the leftmost one (which, however, is only possible on certain platforms). 4. The maze itself is different. The size seems to be about the same (8x32), but in the arcade, the top row gets repeated 4 times with different enemies, which isn't done in the SG-1000 version. Many of those enemies (for instance, the tree throwing apples if I recall it correctly) don't exist at all on the SG-1000, but there are still many elements from the arcade present on the SG-1000 which don't exist in the CV and Atari 2600 versions, such as the ice coming down from the ceiling, the face breathing fire, and the lorries going down ramps. Overall, the SG-1000 version is nearer to the arcade than to the "original" Activision version, but it still has a different maze layout than all of those. So I think Pitfall II on the SG-1000, while having the same name, is quite a different game than the CV version. The question is if it's different enough...

Just dug out this thread out of the "Enormous Homebrew Thread Repository" and wondered what kind of quality the frames would have on a 2600. Hmmm... if you have 30 frames per second, you could try to do it with playfield graphics, changing both foreground and background colors in every scanline. I don't know if it would be possible to change both color registers and rewrite the full width of the background in each scanline... but if it was possible, you'd need 7-8 bytes per scanline, with 200 lines on screen that's 1400-1600 bytes per frame, or 42-48k per second. How good could such a frame look like at all? Maybe something like this...

I tried your "protoype" too on an Emulator. Looks very promising... considering the fact that the Colecovision (like any TMS9918 based system) is only able to do 4 sprites per scanline. But "Wild Western" already has got a "flicker logic" built in to work around this problem. You'll see what I mean if you line up your cowboy with one of the enemy cowboys and the smoke of the locomotive. I think the best thing about the arcade original was the music... this was the first version of "(Ghost) Riders in the sky" I heard, and it sounds pretty good, although it's rather short. The way it's played reminds me a bit of the group Hot Butter. Their biggest hit was "Popcorn", but on their LP they also have some country tunes played in a similar fashion, like "Apache" for instance. They don't cover "Riders in the sky", however... I think the music should be doable in a similar fashion on two of the sound generators. If you use the noise generator for the trippling horses (which tripple in sync with the music), the 3rd sound generator should be free for the sound effects.

Toy Bizarre certainly borrows some elements from Mario Bros. Actually, I'm surprised to hear it was only released on the C-64. The graphics looked rather mediocre for the 64, I always thought they drew the enemies that way so that they could be reproduced easily as color-striped players on the Atari 8-bits or even the 2600. Dino Eggs, in comparison, looks like it has been ported from the Apple II, but the C-64 version seems to be far more popular.

I'm not entirely sure now... as far as I remember, the 520ST was already out in late 1985 here in Austria. But I could be wrong... anyway, I totally forgot about the Amstrad / Schneider CPC which definitely already came out in 1985 (or even 1984) and also had 16 color registers... but only out of a palette of 27!

Technically, no. It has 8 control registers and 1 data register. Maybe what you're referring to is the color table in Mode 0 (Graphics Mode), which is located in video RAM and may start at any byte location which is dividable by 16 (256 different possible locations). But this one has 32 entries of one foreground and one background color each, setting the color for 8 consecutive character definitions. That's the 5 MSB's, not the 4 one, as far as I can see. If that's nuisancesome depends on the type of display you want to achieve. If the objects with the same shape should all appear in the same color, you're fine off... you set the color once and don't have to manipulate it anymore if you place the same object elsewhere on screen. However, if you have objects with the same shape which should appear in different colors, you have a problem. I think that's one way the technical engineers tried to achieve "color" on screen with the least RAM used possible, to the best result. In this case the colors are tied to the character definitions, so each set of 8 defined characters get one foreground and one background color, which gets used anywhere that character appears on screen. In contrast to that, on the C-64 (and on the Pac Man machine, for that matter), you always have to write two bytes to define one character... one for the actual character, and another for its color (or, at least one of its colors... depending on the mode you use). This, of course, gives you the flexibility to put the same characters on screen in different colors. But the C-64's color RAM is 1000 bytes... same size as its character RAM, where as the TI chip's color table is only 32 bytes. So, at least for mode 0, they made it to implement color using only 32 additional bytes. I still like that method better than the one on the NES, which only lets you select 1 out of 4 4-color palettes (with the same background color for each) for each block of 2x2 characters (16 pixels), so that you really don't get too colorful pictures out of this. To better understand that greed, maybe you should know that the unexpanded TI-99/4, which the chip initially was designed for, stores BASIC programs in the video RAM, since there are only 256 bytes of CPU RAM in the system. Thus, 32 bytes used for color saves you 736 bytes for your BASIC programs over the 768 bytes a full color RAM would have taken.

I think it is significant that both the MSX and the SMS/Genesis were derived from the TMS9918. But I still think TI should have put in some palette registers. Should have.. should have... but they didn't. In fact, back then no computer or video game did have 16 color registers to choose out of a palette (at least no affordable one!). There basically were two approaches to the color problem: 1. a bigger, fixed palette or 2. an even bigger palette with color registers selecting from it. The C-64, the Intellivision, the Odyssey^2, the TMS9918 (whichever machine it was used in), the VIC-20 and the ZX-Spectrum all followed approach 1, and mostly had 16 colors available, which lets you store foreground and background colors of a character in one byte - and they typically have character modes where you can choose foreground and background colors for each tile (character) (except for the Odyssey^2 which doesn't have fixed tiles, only a grid for background graphics). The Atari 2600, the Atari 400/800 and the Bally Professional Arcade followed approach 2. The 2600 has 4 color registers and a pallette of 128 colors, the Atari 400 has 9 out of 256, and the Bally (I think) 4 out of 128 (or was it 256?). No machine of that era hat 16 color registers! The first machine that had 16 or more color REGISTERS was the NES with 25 colors (13 for background tiles, 12 for sprites) out of 64 (+ Tricks), and the first home computer I know of having 16 color registers was the Atari ST. This was topped by the Amiga having 32 out of 4096 (+ HalfBrite + HAM modes for more), interestingly improving on the Atari 8-bit's graphical architecture (which was in turn improving on the Atari 2600's architecture). Before that came the Atari 7800, but as far as I know, it also has only 13 color registers (to choose out of 4 4-color palettes sharing the same background color). Arcade machines are a different story, of course. The Pac Man machine, for instance, uses a far more complicated scheme than all of the computers or consoles of its era (the single color value of a character or sprite selects one of many 4-color sets, with each of the 4 colors of the set pointing to a 32-entry lookup table defining colors out of the "actual" 256-color palette - OK, maybe the NES comes close, but not quite), with subsequent arcade machines following similar schemes, only improving on the number of colors in a palette, the number of colors actually possible for each pointing layer and the number and size of layers and sprites displayed.

Wonder what TI had in mind? Wonder why the part no. starts with TMS-99? Well... I suppose what TI had in mind was what the chip was first used for... the TI-99 home computer, which happened to be the first computer I had. And that one already was developed in the late 70's. And it was supposed to be a home computer, not a game machine, yet TI put out some pretty good games for it. Atarisoft did, as well - they only weren't good at doing music. It also had the same sound chip as the Coleco (and many arcade games of that era, for that matter), only running at a slightly slower clock rate. OK, so the graphical results weren't that good, but many home computers of that era were far worse off... having no sprites at all. So you could say that the TI chip catered more for gaming applications than other chips of that era. I think the only other home computer out in that era who had something resembling sprites were the Atari 400/800, which had player/missile graphics. But those were also monochrome and basically only 8 pixels wide. And you also only had 4 of them per scanline. But what's worse, the Atari couldn't manage more than 4 sprites by itself... you had to rewrite the sprite locations on specific raster lines to get more independent sprites... the TMS9918 does that for you, for up to 32 sprites. Not even the C-64 has that many sprites. OK, you get 8, and those are bigger and multicolored if you want. And you can display all of them in one scanline. But to get more than 8, you have to do the same like on the Atari's... Background graphics wise, it's hard to judge who leads. OK, you do have a 4 color mode on the Atari 400/800. And you get to chose those 4 colors out of a huge pallette of available colors. But if you do hi-res graphics, those 4 colors are the same for the whole screen! (OK, you can change those too per scanline by clever programming, of course) If you compare it to other video game consoles of that era... there's none with multicolored sprites, except for the NES, but here in Austria, the NES wasn't released until 1987, that's 4 years after the Colecovision. So the Coleco's competitors at that time were the Atari 2600, the Intellivision and the Magnavox G7000 and (in Europe) G7400 / Odyssey^2 (in the USA). And those consoles all don't allow for multicolored sprites. The Atari 2600 does have a huge pallette, but only 4 color registers shared by the various objects. The G7000 can display many freely moveable characters on screen, but all of them are only 8x8 pixels, and only 4 of them are freely definable. The Intellivision is best off, even having scroll registers, but its background graphics only have half the resolution of the Coleco's, and it also works with a fixed 16-color pallette (as far as I know). Below I've created an example of what you can do on a TMS9918 in bitmap mode, with clever color mixing.