DanBoris

Yeah, it's a teqnique that wasn't used much (at least not on the 5200), but Activision used it in some of it's ports, like Kaboom. Presumably to make it easier to port from the 2600 version. Dan

Yes, it is a shame they took out the sprite duplication, but I wonder if you could play some tricks with the GRAFP0-GRAFM registers? These work just like the PM graphics registers on the 2600 in that they write the image data directly to the player graphic register, thus bypassing the ANTIC. You would have to write them on every scanline, but you may get a little more flexibility then with the normal way of handling PMs.

Yes, they do have color, but you happen to pick three games that didn't have much color to them, they scarificed color for higher resolution. Try some more games, most do have more color then those 3. Dan

I got so interested in this topic that a hacked up a quick demo of how sprite re-use can be done. It's just a modified version of my 52pm demo. You can get it off my web site at http://atarihq.com/danb in the 5200 section.

Cafeman: You are correct in your reponse about the flicker, they sometime do combine both methods. If the players are far enough apart you can do re-use, if they are near each other you can do page flipping. I am not sure exactly how games handle the sprite re-use, but here is an idea. You can probably do most of the work during the vblank. Vertical position can definitly be handled during vblank, the data can be written into both vertical locations it's going to appear at. You would probably then want to have a DLI on every line (or one every few lines depending on the mode). The DLI could check a variable setup during the vblank that indicates on which line the horizontal position of the player can be changed. Dan

The four port uses - 9.3V [email protected] amp and the two port uses - 11.5V [email protected] amp An NES power supply will not work, since it outputs AC power not DC. Dan

There are two ways to achieve this: 1. The easy, ugly way. With this method you display 4 sprites in one frame, then before the next frame you move them to represent 4 different sprites. This is quite easy to implement but it results in some flickering. 2. The hard, but clean way This is sorta what you described. If you have a sprite that is shown at the top of the screen, you can move it once it's drawn to the bottom of the screen so it's displayed twice. Implementing this can be tricky. The re-use obviously can not occur if the two sprite share any horizontal lines. It also won't work if one sprite is slightly below the other since you won't have time to move it. This technique works especially well when you know certain sprites will only occupy certain parts of the screen. For example a space invaders type game, the ufo that goes across the top of the screen and your base at the bottom could easily be the same sprite. One other thing to not forget. There is a bit that can be set in one of the GTIA registers the combines the 4 missiles into a 5th player. So if you don't need the missiles, you can get a bonus sprite. Dan

The spill over into the next scanline is really the only ill effect of running to long in a DLI. If you try to stuff the video registers while the line is being drawn you may get som strange results. There are actually times when you might want to stay in a DLI. For example the Atari logo screen that's in the 5200 BIOS enters a DLI at the top of the logo, and stays there incrementing the color register for each scan line. That's how the rainbow effect is achieved, it's just one long DLI. Dan [ 08-08-2001: Message edited by: Dan Boris ]

1. There is no real trick to this, just define each player with the appropriate part of the image and position them so they appear as one large image. There is one trick you can do. If you set bit 5 of the PRIOR register to 1, then the overlap of players 0/1 and 2/3 will produce a third color. So this allows you to produce 4-color players using only 2 players. 2. I assume your text areas are going to be character modes (like mode 2), since you can mix modes using the display list this is the way to go. As Eckhard said, using BCD is a good idea, and makes updating the score very easy. To draw each 2 digits, you would first mask off the top 4 bits, shift then down to the bottom 4 bits and add them to 16, which is the character code for '0', and put this into the screen memory at the correct location. You would then repeat this process with the bottom 4 bits of the original number. Dan

You can use PM's in any graphics mode. How they appear in relation to the background is determined by the priority registers. You can give certain color registers priority over the PM's so they will appear to go 'behind' the playfield. Used carefully this can be a really cool effect. As for creating re-defined character sets, there where a couple great character re-definition tools written for the 8-bit computers. You can probably find these on the net, run them on an emulator, then just write a program to convert the output file to source code. Dan

According to Atari-History.com, the 3600 name was used for a couple prototype systems. There was a successor to the 2600 called a 3600 but this project was scrapped. The 7800 also started out being called 3600.

Since you are only getting a black screen on all the different games you try, it doesn't sound like dirty cartridges, these usually result in random displays on the screen. If you are getting snow on the TV when the game is off, then a black display when it's on, then you are getting power to the 2600. You may want to open up the 2600 and make sure the IC chips are pushed firmly down into thier sockets, loose chips could cause this problem. Also, a note on cleaning cartridges connectors, using sandpaper is not a good idea, to abrasive. The best best is alcohol on a towel or q-tip. If this isn't enough, try a pencil eraser, then repeat the alcohol cleaning. Dan

This is a result of how the cartridge was originally dumped. 5200 carts have space for 2 ROM chips in them, 16K each. So if a cartridge had only a 16K ROM in one slot then the remaining 16K would either be blank of contain garbage. From what I have seen there were a couple different combinations of chips that where used in the 5200 cartridges. Dan

I finally got around to tracing the circuit for the 5200 Trackball controller and have posted it on my web site http://atarihq.com/danb in the 5200 section. It's actually a pretty cool circuit that converts the speed of the balls rotation (derived from digital encoder wheels like in a mouse) into an analog voltage level which is fed to the console. The result is that the speed the ball is rolled in a specific direction is analagous to the distance you push the stick in the direction. Dan

You can "sorta" do this, due to an anomily called color artifacting. In Antic mode 2 (and 15 for that matter) the pixels are so small that they are less then one color-clock wide. The result of this is that if a pixel doesn't have one on either side of it, it will show in a color instead of white. The pixel will either be green or blue/purple depending on whether it's in an odd or even column. With some carefully created graphics this can be used to great effect. I specifically remeber this being used in the Atari 8-bit versions of Ultima. Dan

I have always tried (and succeded) to avoid E-bay, I much prefer finding my games in the wild. I have over 250, 2600 titles and found 95% of them at flea markets and yard sales. At my local flea market I actually found a 2600 Crazy Climber and Waterworld, for $1.00 each, and just a few weeks ago a find a complete Bally Astrocade with a couple games for $10.00 at a flea. So the good finds are out there. Dan

The 4 port 5200 is much rarer then the 2 port so I would assume it's worth more, epscially if you also have the special TV switch box the 4-port needed. Dan

Can't wait to see what you come up with for the Jr schematics. It will be interesting to compare them against the 4-switch schematics to see what has changed. I would love to create a page with the schematics for each model and board rev. to see the differences. Dan

Those two would definitly be among the most numorous since they where both pack-ins with the 2600 system. Combat was the first and Pac-Man the second. I wonder what would be the most numorous after these two? I know from my own collection that Asteroids and Space Invaders where both very popular, I have accumulated a bunch of both of these over the years. Dan

Here's a perspective on discovering atari 2600 emulation from the other side of the fence. I discovered emulation in mid '95 when I discovered Marat F's Gameboy emulator. I played around with the source code and that got me interested in emulation programming. I had also discovered the Stella docs around this time and tried to do my own 2600 emulator which didn't go anywhere. I then discovered the 2600 emulator x2600 by Alex Hornby. I took the source for this and produced a DOS port called Virtual VCS. VVCS became the first non-commercial (Activision Action Pack where already out) 2600 emualtor for DOS! Another DOS 2600 emualtor (Stella 96 I beleive) came out with a few weeks, ultimatly to be followed by quite a few more. I also distinctly remeber some heated debate shortly after the Action Pack came out as to whether it was an emulator or not. Dan

You can get some info on this here: ftp://kew.sel.eesc.sc.usp.br/Electric/Atari26 00/SRAM-Cart/

This might be as simple as just a dirtly cartridge connector. First try cleaning you caridges (alchohol and q-tips are good for this). Next try cleaning the cartridge contacts in the unit, this can be a little tricky but can be done. If that doesn't work, try taking the system apart and pushing the IC chips firmly down into there sockets. I have found that these steps will fix a majority of problems with the 2600. Dan

Hello, I'm the one who did this "BLASPHMEY of a coding job" There is a good reason there is only one 7800 emualtor, this system is a pain to emulate and there is very little tech info out there on it. I got the tech info for the system a few years ago and passed it onto two other people to write the emu (since I had to many other projects on my plate), but in the end, ended up doing it myself. Altough I say it myself, I think they quality of the emulation is quite good considering what I had to work with. Colors are always a big problem since with console systems there is rarely an objective way of determining "correct" colors. The only way to really do it is to observe the real game, determing the curresponding color code in the emulator and tweak it until it looks correct. This is a VERY tedious process. As for the frame rate in MESS, 6fps seems a little low to me unless you have a really old computer. The 7800 emulation does require a pretty hefty machine to run at full speed (the video system is quite complex to emulate), but it should run ok on even an average system by todays standards. "At least the 2600 emulation community has a true love for the games and isnt just interested in emulating more than one console" I DO have a true love of the games, and the machine. Most of the systems in MESS are maintained by a single person, so each does get personal attention even though they are all in the same program. People often ask my why I stopped writing my standalone 7800 emu and moved to MESS. For a programmer it's quite simple. MESS provides the entire infrastructure for writing an EMU so I can conentrate of just coding the emulation and not have to worry about all the details of handling video modes, sound cards, file loading, differnt type of controllers, etc. Plus by putting it in MESS I get automatic cross platform support. My standalone was great if you where a PC user, but you were out of luck if you had a MAC. Dan