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DanBoris

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Posts posted by DanBoris

  1. Posted

    For Cafeman:

     

    1. Multi-color Overlapping players. This was my first priority in the new version and I already have it working great. Does anyone know how this effects missiles?

     

    2. Colors. The color palette is a major problem. I setup an 800XL next to my PC and compared the colors are you are right they don't match. The real colors seems to get brighter faster then the emu, and the at luminance 15 they are almost all white on the real hardware. My problem is tweaking them manually would be a nightmare so I need to find a formula to calculate the whole palette.

     

    Debugger: I look into adding a break when a certain address is changed.

     

    For Debro:

    The debugger can already do what you ask. Just type R 4014 and it will start executing until it gets to address $4014. VSS .80 already support 8K and 16K ROMS.

     

    Dan

  3. Posted

    Building a cart dumper is not a trivial task. If you really want to do it, the easiest solution would probably be the one on this page:

    http://quadrun.tripod.com/

     

    Which is built from an Atari 7800 (which might be the one mentioned above). This will dump both 7800 and 2600 carts. It would be very hard to build a device like this out of a 2600 since it doesn't have a BIOS ROM or extra RAM to put the dumping code in.

     

    You could build something from scratch but this is tricky. Probably the easiest way would be to buy an EPROM reader/programmer and make an adaptor that connected the EPROM socket on the programmer to the cart.

     

    The 2600 cart dumper I built a long time ago was built on an PC ISA card with a peripherial interface chip.

     

    Dan

  4. Posted

    First, DON't use a wet (with water) rag.

     

    You really don't need to do an over all cleaning of the board, there are certain key areas that need to be cleaned.

     

    If it's just dusty blow it off 'manually', or with some canned air, or an air compressor. Next clean the cartridge slot with some alchohol. The best way I have seen suggested to do this is to wrap a tissue or paper towel around a thin piece of cardboard and wet that with alchohol.

     

    Finally you can clean bad connections between the chips and thier sockets by very carefully removing and re-inserting each chip.

     

    These tips will solve many problems with the 2600.

     

    Dan

  7. Posted

    When the 6507 processor in the 2600 resets it reads whatever address is stored at memory location 1FFC/1FFD and then jumps to that address to start execution.

     

    As mentioned above .ORG simply tells the assembler the origin address of you program. So if you have this in your source code:

     

    .ORG $1000

     

    start

    jmp start

     

    "start" is a label, so the assembler would know that start=$1000. When it assembled the jmp instruction it would be assembled to jmp $1000.

     

    One other thing to note about the 2600. Since the 6507 processor only 13 address lines, the highest memory location it can access is $1FFF. But this doesn't stop you from putting your code at $F000. If the 6507 encountered a JMP $F000 for example, the top 3 bits of the address would be dropped and the jump would go to $1000 instead.

     

    Dan

  8. Posted

    /RES = Reset. Pulling this low resets the processor.

     

    RDY = Ready. When RDY goes low, it essentially stops the execution of instructions by the processor. This is usually used when a device takes longer then usual to read or write data. When the processor attemps to write to a slow device, the device will pull RDY low until it has actually written the data.

     

    O0 = Phase 0: This is the master input clock to the processor

     

    O2 = Phase 2: This is an output clock from the processor that is derived from Phase 0. It is used to synchronize read and write to external devices.

     

    Dan

  12. Posted

    Here's my most inspirational "in the wild story". There is a local flea market that I went to every weekend, and there is one stand that always had a bunch of commons, which rarely changed. They where in bins with a bunch of them upside down, so I one day I stared going though them turning over one Combat and Space Invaders after another. About 3/4 of the way through I was just about to give up and walk away, but something made me flip over a few more carts, and low-and-behold I flip over an Atari cart and it's Swordquest Waterworld! Got it for $1.00.

  13. Posted

    I think the major reason is that up until very recently there wasn't much information on how to program the 7800. The other problem was the encryption key for the carts. Until late last year there was no way to generate these keys, so there was no way to produce real carts that would run on an un-modified 7800.

     

    There are some people doing 7800 development, and I think once people start learning the system, there will be more new games developed for it.

     

    Dan

  14. Posted

    Two possible problems. First are you clearing PF1 at the start of the frame? If not then it will always display the same pattern. Also, if you want to only display on that single line you will have to clear PF1 after that line.

     

    Dan

  15. Posted

    So, assuming you don't use the stack for anything else, you can have 128 nested subroutines. This would be slightly less on a 5200 because of interrupts which also push stuff on the stack.

     

    Dan

  17. Posted

    quote:
    Originally posted by Cafeman:

    Dan, what platforms can I make games for using 68000?

     

    Could you list all that you know?

     

    Why did you learn 68000?

     

    I learned it for my job, so I could write test programs for 68000 based data communications equipment I was troublshooting/repairing.

     

    Dan

  18. Posted

    quote:
    Originally posted by Cafeman:

    I only know 6502 ASM right now, and I'm no expert.

     

    I also plan on learning 68000 ASM someday soon. I know you can make Genesis games with it, and if I'm reading this thread correctly, Jag games use 68000 ASM too. Does the GBA use an ASM language too, or if not, what is the language used for GBA development?

     

    You are going to love 68000 assembly.

     

    I made the transition from 6502 assembly to 68000 a bunch of years ago, and boy was it a dream! After doing 6502 coding, working with the 68000 is almost like programming in a higher level language.

     

    Dan

  19. Posted

    I have programmed in a number of different assembly languages, and I have to say that 68000 assembly is one of the easiest. Of course this is all relative since programming in any assembly language can be a daunting task. Also, programming a system like the Jaguar can be particularly difficult since it's hard to get help on how to do it, you can't go to the store and pickup a book on Jaguar programming so you will have to work out a lot of things on your own.

     

    Dan

  20. Posted

    quote:
    Originally posted by -^Cro§Bow^-:

    Okay Dan,

     

    ...or there is still something amiss in the 7800 driver on Mess for the Pokey support.

     

     

    Most likely this is the problem. It's unlikely that a bad dump would only cause music to be missing. I'll have to find some time to take a look at this problem.

     

    Dan

  21. Posted

    The POKEY is DEFINITLY supported in MESS, I know, I put it there The Pokey emulation in the MAME/MESS core is pretty accurate so the POKEY emulation in the 7800 driver should be complete. I will have to checkout Ballblazer on my real 7800 to see what you mean about the music.

     

    Also, as Eckhard indicated the audio line coming from the cart (where the pokey is) does get mixed with the audio from the TIA so you can get 6 channels of sound.

     

    I have often thought about why Atari didn't include a Pokey onboard. Space was definitly an issue, the 7800 logic board is pretty tight and the POKEY is a 40 pin IC so the would have had to increase the size of the board.

     

    I may have also been for economic reason. Since they would have had to make the board bigger it may have increased the cost more the just the price of the POKEY chip, and at that time, they selling price of a console was a very important issue. Putting the Pokey on the cart on the other hand didn't really hurt Atari much since most carts had either extra ROM or RAM on them anyway (POKEY carts had neither) so the cost to make any supercart would have been about equal.

     

    Dan

     

    [ 02-18-2002: Message edited by: Dan Boris ]

  24. Posted

    As you suspected the problem with this is how much time Maria has to get the data into the scanline. For each scanline you have 456 Maria cycles to generate the scanline.

     

    Each byte you transfer to the scanline requires 3 cycles. If you used the 160x2 mode which would give you 160 pixels across in 4 colors, it would require 40 bytes to cover the whole scanline. So 40 * 3 = 120 + 8 (for the header) = 128 cycles per line. So you could only 3 different graphic lines on one scanline.

     

    Dan

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