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DanBoris

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Posts posted by DanBoris

  1. Posted · Edited by DanBoris

    That's you trying to fix an old system. If it was printed on toilet paper it would have served its purpose.

     

    But for us enjoying classic material, the graphic and font nuances are important. The 70's palettes and curves make or break a scan.

     

    I wasn't knocking the need to accurately preserve the content of the magazine, just making the point that's it also still has useful information in it. I actually have a fairly extensive collection of Byte and Creative Computing magazines and would like to see them accurately preserved with high quality scans.

     

    I will clarify. The information presented in these magazines is not necessary for 99.99999% of the IT industry to operate in 2013. That's was my meaning when I wrote that the "raw information" was no longer necessary.

     

    I'm glad to hear that people are still finding the information necessary. I would love to hear about how this information was necessary beyond personal use. Was someone's life saved? Were jobs or businesses saved? What was done that was necessary, meaning compulsory or required? Please expound, but be aware that repairing a computer to simply make it functional again is a desire and not a need... unless that computer is going to be used for something necessary, like open heart surgery or factory automation or..

     

    Same could be said for 95% of the magazine that are currently sold today.

    • Like 3

  2. Posted

    Because it is 2013 and we're talking about 20+ year old content, I think the presentation (including images, appearance, design, ads, typefaces, all of it in entirety) is just as important as the text. The "raw information" is no longer necessary... we are reading and enjoying these because of the history, not the "raw information."

     

    I have to disagree with the "raw information" not being necessary. I recently acquired a IMSAI 8080 system with a floppy drive that I could find no information about on the Internet. It also had a floppy disk controller that again isn't document anywhere I could find on the net and used an IC chip that I could find no information on either. Digging though some old Byte issues I ran across an article about how to interface this exact floppy driver to a system using the same unidentified chip that is on the controller I have. This information will be invaluable in getting this system running again.

    • Like 1

  3. Posted

    IIRC it also does some sanity checks on the 6502 & other hardware along with the fuji graphic while it verifies the digital signature. There's even a disassembly with some comments: http://www.atariage....es/bios7800.asm

     

    Yep, this is all it does. Once the verification is complete the bios is swapped out for the cartridge ROM so isn't even used after the game starts. So technically it's more of a boot loader then an actual bios.

  4. Posted

    I did a bit more testing tonight. I wired up a power extension cable (3.5mm socket to jack) that let me hook my multimeter into the 9v line (its a 2600 jr type). Results were interesting and a little surprising.

     

    No cartridge - power drawn was 240ma.

    With a cartridge inserted power draw varied from 260ma to 300ma. COMBAT was the most power hungry and the Atari 32 in 1 was one of the least power hungry. I expected the opposite.

    TV on/off - didn't seem to make any difference.

     

    This is by no means conclusive as it still doesn't tell me anything about the cartridge port itself. However as the PSU is rated at 500ma at 9V - so that bit at least will cope.

     

    I'm still hoping the x28c256 will draw considerably less than 30ma (at 5v) due to running at only 1Mhz instead of 5Mhz but I will just have to wait and see.

     

    Roland.

     

    The difference between Combat and 32 in 1 is not surprising since Combat was an early cartridge and the 32 in 1 was much later. Chips generally get more power efficient over time.

     

    Besides the PSU the other thing you need to look at is how much current the voltage regulator in the system can handle.

  6. Posted

    Hello!

     

    Some of you may know from another thread in the 7800 forums that I was working on an Atari 7800 game called "Get Lost".

    It worked wonderfully in emulation, but once people started trying it on physical hardware, a difficult problem occurred.

    On occasion, the screen would go completely black. This is not reproducible in emulation, which makes me suspect that something is triggered only by real hardware.

     

    I have done some thinking, and I have an idea for how to debug this-- I basically need to make something that can "sniff" and record information in real-time.

    Then, when the issue reproduces itself, I can go back through the trace that I have, and try to deduce what went wrong.

     

    I could do this with a logic analyzer, but even to get there, I need some sort of hardware to be able to interface with the cartridges.

    That's when a few ideas hit me, and I'd like to query some hardware folks for some information.

     

    My first thought was to basically make an extendo-cartridge between the 7800 and the cartridge that I would solder some wires to, in order to hook those into some sort of logic analyzer or equivalent place that stores data. There are 32 pinouts on a cartridge:

    http://www.atarimax....g/7800cart.html

    They include:

    - 16 address lines

    - 8 data lines

    - 2 ground lines

    - 1 Vcc (+5V)

    - HALT

    - R/W

    - CLK2

    - EAUDIO

    - IRQ

     

    If I was to make my own "sniffer", I think the pieces of importance are the address and data lines, and the clock.

    So, my first question is... if I made such a cart to get information from these pieces, how do I account for crystal drift in the clock?

    Here's what I mean-- if I monitor oscillations in the clock line, I need to deduce when to read the address and data lines.

    And, there could be very, very small differences in when the clock refreshes vs. these lines.

    Do I need some sort of mechanism to sample the clock only when it's exactly halfway-between oscillations?

    Maybe this sounds crazy, but if I sampled all lines the exact millisecond when the clock changed, I wonder if everything will be ok, or if a circuit needs a millisecond to change a data line, etc. I'm wondering how that's all handled in hardware, as I'm new to this.

     

    My second question is that I was debating whether or not I could just hook in alligator clips inside the atari 7800, and if there was a place where I could read the PC. Is that exposed? Or, is the PC hidden inside of the 6502 hardware itself? I think sampling that might actually get me the data I need a little bit easier than translating data and address lines and mapping them to locations in code. Is that something that's doable?

     

    My third thought is that I was wondering about space utilization. If I sampled a 3 bytes each clock iteration (2 address bytes, one data), and logged it to a file, how fast would it grow? This site: https://sites.google...7800wiki/vblank seems to indicate there are 2166 cycles per frame in a base case. So, 2166 * 3 * 60 frames/second = 389,880 bytes per second. That's 23,392,800 bytes per hour (so, 23M an hour). So, this implies that if it generally takes 1-2 hours for my bug to show up, hardware-wise, I'd need the ability to store at least 100M of data in the miniumum case, but probably I should have a couple hundred megabytes available just to be safe. So, are my calculations correct here?

     

    Thanks for the insight; I have a very limited hardware background, so I'm grateful for any help.

     

    -John

     

    The clock is the key to knowing when to read the data. The address and R/W are valid on the rising edge of the clock and data is valid on the falling edge.

     

    As for your third question, no the program counter is not accessible, it's internal to the processor.

  7. Posted

    Does anyone know the correct way to enable the TIA chip? I know that there are 4 chip selects, CS0, CS1, CS2, and CS3 on pins 24, 23, 22, 21 respectively but many pinouts I see online have different information as to weather they are active high or low. Here are some examples:

     

    http://atarihq.com/danb/tia.shtml

    http://www.atarimax....g/2600ctia.html

    http://amazingdiy.fi...ri2600_tias.jpg

    http://www.atariarch...a/images/38.gif

     

    If anyone knows the correct way to enable it, I'd be very thankful. I'm trying to restrict it's address range to $0000-$003F.

     

    Thanks!

     

    Never noticed the variations in the CS pins on the different sites, glad mine was correct! :)

    • Like 1

  10. Posted

    Very cool times indeed. There were a slew of stand alone arcade emulators. Rygar, Gauntlet, Ghosts'n Goblins, Bombjack, Asteroids, Mr. Do! Series, Pac-Man, Lady Bug, and a bunch of others that all had at least one stand alone emulator, sometimes several. Later on, we saw things like Callus and JAS, System 16 and a few others that focused on a particular set of games or hardware type(s).

     

    I remember those days. I also remember there were people who got very upset when MAME added support for games that where in these standalone emulators. They were sort of accusing MAME of putting these single game emulators "out of business" as it were.

    • Like 1

  11. Posted

    I've collected a lot of 2600 emulators. My copy of VCS2600 has a date of 10/20/1996, but that's the "r7" (release 7?) version.

     

    VVCS was also released in 1996 (v0.60 was dated 07/25/1996).

     

    A26 (v0.15) was also released in 1996 (12/11/1996).

     

    And V2600 (v0.81) was dated 03/25/1997.

     

    I don't know when the initial versions of those emulators were begun or when they were released.

     

    As I mentioned above the second release of VVCS was 6/18/1996, an I don't have a record of it but I am pretty sure the first release was just a couple weeks before that.

  12. Posted

    Action Pack was the first that I am aware of, it was released in June of 1995. I remember back then a lot of people were skeptical at first that it even was an emulator. Next was probably x2600 which is what my Virtual VCS emulator was based on, but I have not been able to find any record of when that project was created, but it was prior to June of 1996. My Virtual VCS emulator had it's second release on 6/18/1996. I don't have any documentation of when the first release was but I think it was only a couple weeks earlier. The first playable release of Stella 7/12/1996. Best I can find PCAE came in late 1996.

    • Like 1

  14. Posted

    CONSOL bit 2, when cleared, causes disables the pots on analog joysticks (POTx=$E4) and puts the trackball into calibration mode (POTx = ~center). It's not involved with keypad reading.

     

    The keypad connection to POKEY doesn't use all 6 bits of the keyboard scanning port, only bits 1-4. This leads to keys being detected multiple times similarly to how addresses are mirrored with incomplete decoding. The START key has the pattern %1100 and so POKEY detects it four times as $18, $19, $38, and $39. This key multiplication is why keyboard debounce must be disabled to read the 5200 keypads. With debounce disabled, the first state of the POKEY keyboard state machine triggers on the $18 key and then on the next state $19 is copied into KBCODE. The state machine runs off the 15KHz timer so another 32 scanlines later $39 is captured and reported in KBCODE. Checking for both key values seems unnecessary, but that's the way the hardware reports it.

     

    I remember this when I was writing my 5200 emulator, since I didn't emulate this behavior initially Star Trek wouldn't work. I believe it's the only 5200 game that looks for multiple key-code values..

  17. Posted

    Wow, I did not know about that requirement for the 7800 for encryption... interesting....

     

    Also for the ProSystem emulator, I believe it is looking for a file with the extension .78a (or something like that), how to I get my DASM output to that format, or is it a simple matter of renaming the file with this extension?

     

     

    Thanks!

     

    A .A78 file is a binary cart image with a special 128 byte header added to it that described the cartridge format. Below is the original specification for the header, although I believe some people have extended it since this version. You can setup some data decelerations at the start of your source file to create the header, or use a tool like 78hdr to add it afterwards. As for the 'encryption', it is necessary for the game to run on an emulator. It's not really encryption, but instead a digital signature attached to the cartridge data which is validated by a routing in the 7800's bios at startup. Without the encryption key the Atari logo will just keep cycling at startup.

     

     

     

     

    To work with this emulator ROM images must have this 128 byte cart header at

    the start of the raw data. This header allows the emulator to know the features

    of the cart thus preventing you from having to use a bunch of command line

    options.

     

    0 Header version - 1 byte

    1..16 "ATARI7800 " - 16 bytes

    17..48 Cart title - 32 bytes

    49..52 data length - 4 bytes

    53..54 cart type - 2 bytes

    bit 0 - Pokey cart

    bit 1 - Supercart bank switched

    bit 2 - Supercart RAM

    55 controller 1 type - 1 byte

    56 controller 2 type - 1 byte

    0 = None

    1 = Joystick

    2 = Light Gun

     

    100..127 "ACTUAL CART DATA STARTS HERE" - 28 bytes

  18. Posted

    Look at PCAE, and z26, and Virtual VCS 0.60, tons of fun from the "Dave's Classic VideoGames" website. They kinda sorta died out. Lots of mistakes and inaccuracies. Who would use them today? No continued development. But still, I have respect for the early efforts.

     

    Wow, can't believe people still remember Virtual VCS. I the case of VVCS, it didn't die because it was inaccurate, it died because other emulators like Stella quickly surpassed what I had done so I saw no point in continuing and moved onto other things.

     

    Dan

  20. Posted · Edited by DanBoris

    I am trying to figure out what this is. These picture came from a friend of my sister and she describes it as "Pong". I doesn't currently work so they only get that test pattern screen, but this at least show's it's a color game so probably early 80's. In the picture of the screen you can see the company name "Rover Leisure Products Co" in Siloam Springs Ark, but Googling that name turns up nothing. Anyone have any ideas?

     

    4.jpg

     

    5.jpg

  22. Posted

    I still have the invoice from my first computer system:

     

    800 16K Computer $679.00

    810 Disc Drive $449.00

    850 Interface $169.00

    410 Recorder $76.00

    Joystick $20.00

    Video Easel $35.00

    Star Raiders $60.00

    Epson MX80FT Printer $559.00

    Printer Cable $30.00

    32K Expansion Board $159.00

    Touch Typing $20.00

    Atari Word Processor $159.00

    Breakout with Paddles $43.00

    Graphit $17.00

    Statistics $20.00

    Visicalc $169.00

    Atari 800 dust cover $7.99

    1 box floppy disks $36.00

    • Like 3

  24. Posted

    I will shortly be upgrading to a new laptop. Before I sell the old one, I would like to "scrub" the hard drive of any and all personal information. A complete reformat of the hard drive would be best, of course, but I do not have the system disks anymore (the hardware is about 4+ years old) and I don't think anyone would buy it without a functioning OS. I'm currently running Windows Vista.

     

    Is there anything available that will completely wipe the My Documents file tree?

     

    There are programs out there that will securly delete files, but the problem is finding all the files that need to be deleted. There are a lot of different places that a file with personal information could end up. Just deleting My Documents wouldn't necessarily be sufficient.

     

    Dan

    • Like 1

  25. Posted

    I'm playing Bounty Bob right now, and I just did a 'head-count' of the number of sprites that are definitely PMGs. I count 6. Now, I know a fifth player can be created by combining missiles, or even 2 small sprites by making 2 pairs of missiles, but these appear to be full size players.

    Am I right in thinking that this can be achieved by creating multiple copies of the sprite image in a single player, then changing the horizontal position of the player by using a DLI? or doesn't this apply to PMGs?

     

    Exactly, it's called sprite multiplexing. Works particularly good for Bounty Bob since the enemies only move horizontally and are always at a predictable vertical location on the screen, so it makes it easy to re-use the players as you go down the screen.

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