R0ger

Why mode 4 ? Every color counts, and you use tiles for the map anyway. You can still move enemies and objects smoothly, with some extra processing. But you have to do the processing in bitmap mode too. You can merge the enemies with background. Again, it's about the same as with bitmap mode. Character mode eats a bit more DMA, and you will most likely need some DLIs (or many), but the extra color is imho worth it. Btw. international karate is in character mode. With shifting and background merging (background being the other character). Games like these will never be 50/60 fps, but you don't really need that.

I think emkay talks about what's usually called artifacting. In hires mode, especially when used with black and white, every pixel has slight color tint. On PAL it's not so pronounced, and the logic of it complex, but on NTSC, it's simple. It's based on X coordinate. If it's odd, the pixel is shifted toward cyan, and if it is even, it's shifted toward magenta. And it's pretty strong. If you want to have white color, you have to use two pixels side by side. As for other differences between PAL and NTSC, PAL has 50Hz and NTSC 60. Both have same horizontal resolution and timing, NTSC simply has less lines visible. VBI is triggered on the same line though. This means, that there is MUCH less time from start of VBI to start of next frame. Generally, you have less time in NTSC, as more time is spent generating video per second. And if your game logic is based on framerate, it will run at different speeds on PAL and NTSC. Then there is different palette. More or less NTSC colors are shifted one hue step up, just check Altirra's color editor, you will understand. Most games are made for NTSC, and they simply run slower, and have wrong colors on PAL. Some games are designed for PAL, and simply don't run on NTSC at all. And few run on both system at the same speed, with the same colors.

I'm quite sure this is Palm OS version. Doesn't meant it would be impossible on Atari though.

I know about quite advanced attempts to port SimCity (from BBC IIRC) but AFAIK it's dead. Will try to get some update on that.

There is another problem with all that complexity. At least in my case it was like that. You will only fully understand the limitations by trying to do something. It's so complex, that nothing you will read will give you correct and complete idea about how it works. You will try to do something, it won't work, and only then you will realize that's what that one sentence was talking about. So all I can recommend is maybe less reading, more experimenting. You should be able to setup PMG or two with few pokes in basic, and then try to use every mode and every register, you get hang of it soon.

Well, the computer will be obsolete when the kid can read .. 😀 Only idiot would use computer like that after 80s. Oh wait ..

Do you already have some game you want to make in mind ?

I'd say the most typical mode for Atari games is 160x200, 5 colors, character mode for background and enemies, and PMG for player character. But it's really not so simple. Most games use some kind of DLIST / DLI trick. Mixing modes is also common. Btw. if you use Altirra (and you should), CTRL+F8 shows you what is made from PMG, and color changes (typically done by DLI). Mode changes (hires / lowres) are pretty much visible without any tool. It's also possible to change modes during the line (side by side) but that's more useful for intro screen. Combinations and tricks are bread and butter. For example, look at my game Sails of Doom: https://atariage.com/forums/topic/283993-sails-of-doom-new-multijoy-game/ The intro screen is horizontal split with hires on left, and lowres on right, with PMG underlay to make the ship silhouette really black (which is otherwise problem in hires). There is also kernel routine (routine which controls hardware registers while the image is being drawn, without returning to main thread), which changes colors every line. The game start menu is in hires character mode, with PMG used for cursor and player colors. The game itself is 4 color lowres in bitmap mode. But the stats above and bellow are character mode hires. All ships and shells are SW sprites, 4 color flags are made using PMG, and the next 4 flags are SW sprites, using same colors as ships and islands. I'd say this is bellow average amount of tricks, at least if you look at modern homebrews. It's not newbie friendly, but I know there are some serious tricks being used on C64 these days, I'm sure you'll be fine. Just analyze everything you see, and don't be afraid to ask. As for docs, the holly grail is Altirra hardware manual, and for basic info I use standard wikipedia for ANTIC and GTIA. But it's a reference, not guide, and certainly not tutorial. I learned most of the things from my friends, so can't really help you here. Experimenting with G2F should get you started, but it has its own quirks.

That reminds me when I was making my own mindlink for Amiga. It used operational amplifiers, with +12 and -12 V from the Amiga. Since then I know, that when you apply what's basically 24V difference over moist electrodes to your forehead, you will see nice flashes. Without pain or any sensation at all on the skin itself !

6502 is simple. That's why doing most of the thing in it is hard. But that's the fun. At least for me it is.

I played the PAL version only, and I thought PAL version is the buggy one. It certainly feels impossible 😁

Wait, there is ANY playable version ? Nice screen and all, and the 'thing' has nice music, but calling it a game ?

That's what I wanted to hear. Won't have time to experiment with it too much though.

Those MP3s are from real hardware ?

Interesting. You have to reset Altirra settings sadly. I had the same issue.

At the moment I don't know about anything which Altirra doesn't emulate. I haven't tested some of these thing of yours though on real hardware. Might be useful if you report any discrepancies.

Pavros syncs timers to polynomial generators. For full control over PWM with filter you need something different. You need to sync 2 channels to each other. Typically you will sync 1 and 3, and use "high-pass" filter on those. You can use STIMER, or setting frequency to 0 for some time. That time can be greatly decreased by setting channel 1 and 3 to 1.79MHz source. That can't be done with channels 2 and 4 though. After you reset both channels, you set them them to different frequencies for some defined time. During that time the phases of the two channels will gradually shift away from each other. You can control how much by the frequency difference and the time. Then you set them to the same frequencies.

Two tone can't get you variable duty cycle. Not with full control. And you certainly can't control duty cycle every period of your high-frequency signal. And if you are willing to change something every period of your base signal, you can set amplitude directly. It's called soft-synth and it can do sine with no problems. Except it takes all CPU power.

Does it even matter what it means ?

$10 in AUDCTL is not really a filter. It just merges channels 1 and 2 into one 16 bit counter. You are right though, it does create special sound. Whenever the low byte goes to 0, it flips channel 1. And when the whole 16 bit number hits zero, the channel is reset. So basically if you set frequency $140 ($40 in audf0 and $1 in audf1) you will get one pulse of length $40 and another pulse of length $100. The low byte controls length of the first pulse, the high byte controls number of $100 long pulses after that. With $A0 distortion it's best used with normal 64k. Not sure how it can be useful in music, but it might add some flavor to the bass. Can't see how RMT could be easily hacked to test it though. I need 16 bit tables for 64kHz, and different AUDC settings, compared to what RMT normally uses.

Don't understand the reverse 16-bit thing. What setting does it use ?

The most important are: view / filter mode / bilinear system / configure system / video / scalines system / configure system / video / pal artifacting (low is cleaner, high is more realistic, and needed for phase artifact effects) Then view / adjust screen effects. Scanline intensity I set to 0, distortions to 0. Bloom is the magic option IMHO. Start with 0 treshold, 0.5 radius, 0.5 direct and 0.5 indirect. Increase treshold to make dark areas darker, mix direct and indirect to achieve desired sharpness. It's also good idea to adjust colors in view / adjust colors. Like boosting contrast and saturation a bit, or adjusting gamma.

Altirra emulates old screen pretty well. You just have to fiddle with it a bit 🙂

That was .. painful 😁 Can you share the XEX, so we can listen to the bass alone ?

What would it be good for ? What you asking is basically pseudo random number generator. Pokey's RNG is hard to predict, that's it's main feature. Predictable RNG can be easily made in software. Or as anti-piracy measure ? That could work. But then Altirra can emulate even that, and if it can't at the moment, Phareon will eventually fix it And these days you want your games to be able to run on emulators anyway.