Jump to content
Have You Played Atari Today?
2600|5200|7800|Lynx|Jaguar|Forums|Store  

DanBoris

Members
 View Profile  See their activity

  • Content Count

    1,086

  • Joined

  • Last visited

Posts posted by DanBoris

  3. Posted

    It's highly unlikely that the 6507 would work at all at that speed. The fastest full 6502's back in the day only ran at a max ot 4Mhz, and I bet the 6507 was rated slower then that, probably 2Mhz.

     

    At best the chip wouldn't function properly, at worst you would burn it up.

     

    Dan

  4. Posted

    Ok, here is some advice from someone who has worked on a 2600 emulator...

     

    First be sure you have read an understand all the Stella documenation you can find, specifically the Stella programmers manual. You can get links to most of this at my site http://atarihq.com/danb

     

    Next, it sounds like you wrote your own CPU core, if so be sure you are counting cycles absolutly correctly. Be sure each instruction has the right cycle count and that you implement the instructions that have variable cycle counts the correct way.

     

    When you are emulating the TIA you have to do it on a cycle by cycle basis. You need to keep track of exactly where your "virtual electron beam" is on the screen so that any write to the TIA registers can take effect immediatly. You also need to know when during a scan line things happen. For example, when you write to the playfield register, at what point does this effect the display. This information is not really documented anywhere that I know of. You may be able to find information in the Stella Programmers Mailling List archive, there is a link on my site to it.

     

    If you need anymore info, please feel free to ask.

     

    Dan

  5. Posted

    Bounty Bob works like this:

     

    4000-4FFF: ROM #1, 16K bankswitched in 4K sections. (use 4ff6-4ff9 to access)

    5000-5FFF: ROM #2, 16K bankswitched in 4K sections. (use 5ff6-5ff9 to access)

    A000-BFFF: ROM #3, 8K non-bankswitched

     

    any accesses (read or write) to the the ranges 4ff6-4ff9 or 5ff6 - 5ff9 will cause the bankswitch.

     

    The logic for this shouldn't be too hard to implement, and since the 5200 carts are so large there is plenty of room for the extra logic chips.

     

    Dan

  6. Posted

    Do you have one of those TV's that switched to a blue screen when it doesn't get a signal? If this is the case then it's likely that you are not actually getting a signel from the 5200 to the TV.

     

    Dan

  7. Posted

    There are a couple major differences between the 5200 and 400/800 hardware.

     

    1. The biggest difference is the controllers. The 5200 has no keyboard, but instead reads the keypads on the controllers through the keyboard input. The 5200 also doesn't have digitial sticks, the 5200 sticks are read like paddles on the 400/800. So controller routines would have to be re-written to port from one to the other.

     

    2. The 5200 has not have a BIOS like the 400/800 (it has a small one but it doesn't provide you much). So if a 400/800 games uses a BIOS call it would have to be re-written.

     

    3. The ROM, RAM, GTIA, and POKEY are at different addresses ranges on each system, so these would have to be resolved.

     

    So to do a port in either direction you would have to disassemble the game, make any necessary changes to accomodate the above issues, then re-assemble it for the other system.

     

    Dan

  8. Posted

    On a normal 5200 joystick the further you push the stick in a specific direction the higher (or lower) the value that you read from the sport.

     

    The trackball on the other hand is based on speed. The faster you rotate the ball the higher (or lower) the value that you read from the port.

     

    Dan

  10. Posted

    Yes, Steven Kent's book is also a very good one. Some people may have read it under the title "The First Quarter".

     

    .. and since we are recommending books, I've been reading High Score, The Illustrated History of Electronic Games by Rusel Demaria and Johnny Wilson. This is another great book that focuses heavily on computer games which is an area that doesn't get a lot of coverage in other video game books I have read.

     

    Dan

  12. Posted

    At lot of very interesting things went on on behind the scenes in the videogame industry back in the day. I would recommend the book Phoenuix: The Fall & Rise of Videogames if you want to read more about it.

     

    One of the interesting things about Atari that I didn't know until recently was that Nintendo originally want Atari to sell the NES outside of of Japan, but (obviously) the deal eventually fell through.

     

    Dan

  15. Posted

    Can you start from 15, decrese it each time and when 0, change the LMS and reload it with 15 again?

     

    This is exactly how you do it.

     

    To scroll from left to right, increment HSCROL, if it's > 15, set it to 0 and increment the LMS

     

    To scroll from right to left, decrement HSCROL, if it's < 0, set it to 15 and decremenet the LMS

     

    Dan

  16. Posted

    If the schematics on my web site are correct then that is a very important capacitor. It's in the power regulator section and you probably won't get the correct voltage to the system without it.

     

    Dan

  20. Posted

    I don't get it.  I didn't think that a binary could start with a "0", using the counting I just wrote.  

     

     

    It's traditional in binary to pad binary numbers out to an "even" number of bits. Since 1 byte is 8-bits, it's common to pad out to 8-digits. So 3 in decimal becomes 00000011. It's also common to see binary numbers padded to 4 digits which is called a nibble. The nice thing about breaking numbers into blocks of four digits is that it makes conversion to hexdecimal easier, because each group of four bits becomes 1 hex digit:

     

    1111010000111000

     

    1111 0100 0011 1000

    F 4 3 8

     

    $F438 in hex

     

    Dan

  21. Posted

    I haven't been able to find any info on bank switching for the 5200 carts. why not go all the way and make a board that will take a 27040 chip or something and get some really great stuff going since the price difference isn't too much betweeen 27256s and 27040s

     

    There was only ever one 5200 cart that used bankswitching, Bounty Bob Strikes Back. You could probably come up with your own bankswitching scheme quite easily, and there is plenty of space inside a 5200 cart to implement it.

     

    Dan

  22. Posted

    This isn't that hard. If a program runs well in emu, it usually runs well on real machine.

     

    Unfortunetly, this is not at all true. Actually the reverse is far more correct, if it runs on the real hardware, it should run well on the emulator.

     

    The reason for this is that there are certain things that aren't necesarry to emulate to get existing games to work. For example, on a real 5200 if you don't enable the keyboard scanning you won't be able to read the key pads or controllers. On my 5200 emulator, I never emulated this behavior because there was never a time when a game needed to have the scanning disabled, so reading the controllers works on the emulator whether you enable keyboard scanning or not. This tripped up a few 5200 programmers who where developing using just the emulator. This is just one example, there are many others.

     

    Dan

  23. Posted

    I would recommend an APE interface:

     

    http://www.atarimax.com/

     

    This cable and software allows you to hook you Atari 8-bit to a PC and use the PC like a giant disk drive. This will allow you to easily access your files on both the Atari and your PC.

     

    As for a language to use, Atari Basic is a good choice to get your started. It was actually quite powerful and was even used for a number of comercial games back in the day. The only problem is that you won't be able to use it to make a cartridge based game, for that you will need assembly language.

     

    There are at least 2 assembly language carts that I know of. The first was the Atari Assembler, and the other was Mac65 by OSS (which also comes in a disk version). From what I can remeber Mac65 was the assembler of choice for the Atari, much more capable then the Atari Assembler.

     

    Another option is to write your code on a PC and use a cross assembler (an assembler that runs on the PC but in this case produces 6502 binary code). You could then run the game on an emulator and/or the real system via the APE interface i mentioned above.

     

    Hope this helps

    Dan Boris

  25. Posted

    I use my NES AC adapter. I had to install a new connector into the back of the unit, but it works great.

     

    I wouldn't recommend doing this. Although they are the same voltage (9V) the NES adapter out is AC then 7800's is DC. It guess it works, but it's not good for the system.

     

    The specs on the 7800 adaptor are:

     

    Input: 120VAC 60Hz 15W

    Output: 9VDC 1Amp

     

    A replacement with these specs is not hard to find (I belive you can get them at Radio Shack), the problem is the connector. The connectors are hard to find but I have heard that they are used on some portable phone batteries. The other option is to modify your 7800 to put in a more standard power jack.

     

    Dan

AtariAge
Forums
Store
General
Follow AtariAge

Copyright ©1998-2021 AtariAge

×
×
  • Create New...