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Bryan

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Everything posted by Bryan

  1. I suppose, but it would have been another 6502 computer in 1984, right as 68000 machines were hitting the market. It might have had an impact overseas but I doubt it would have ever been a big seller here.
  2. Well, that's kinda why I offered the Kit, so people could flip things around any way they wanted. For most installations, the top mounted jumpers are much easier to get to and the green terminal is still the highest thing on the board. If you flip both the terminal and the jumpers to the other side, then it should work well mounted on a socketed 4050. Once I get the 4050 boards in, I'll post pictures of them in use.
  3. Yeah, it was a good and a bad decision. The 1200XL was the baby machine of the new line and yet it was priced at $900 despite being cheaper to build than the 800. I think Atari was dazzled by the prices Apple was getting.
  4. Because of the 5200 reset issue, I'm making a small 4050 add-on board I'll send out for free to those wanting one. Basically, if the 4050 is socketed (this seems to be mostly 4-ports) then the only way the Plug-In board fits under the shield is to remove the 4050 which causes problems as the 4050 also handles the reset signal. The options are to solder the 4050 in (either by removing the socket or soldering it onto the UAV or the bottom of the motherboard) or building a low-profile version of UAV using the Kit. This LP version could have the terminal and jumpers soldered under the board instead of on top. If there's ever a new revision (some day, I hope), I'm going to include the 4050 functionality on the UAV itself and make it a little easier to have manufactured.
  5. Today I'm getting another batch of orders out and getting caught up on PMs. If I juggle too many orders at once, I tend to get confused. Because of the 5200 reset issue, I'm making a small 4050 add-on board I'll send out for free to those wanting one. Basically, if the 4050 is socketed (this seems to be mostly 4-ports) then the only way the Plug-In board fits under the shield is to remove the 4050 which causes problems as the 4050 also handles the reset signal. The options are to solder the 4050 in (either by removing the socket or soldering it onto the bottom of the board) or building a low-profile version of UAV using the Kit. This LP version could have the terminal and jumpers soldered under the board instead of on top. If there's ever a new revision (some day, I hope), I'm going to include the 4050 functionality on the UAV itself and make it a little easier to have manufactured.
  6. Are you sure that's not the attract mode/screensaver kicking in? Does pressing a key make it stop?
  7. Well, others have pointed out that the sounds are free (that is, no extra code involved since Pokey's using those channels). But the question you're asking is the aesthetic one. I've debated many times whether it was a good feature or a bad one. In the end, I think it comes down to two things: 1. The purchaser of a 400 or 800 had probably never owned a computer before. The sounds wouldn't be unwelcome because you wouldn't know any different. 2. Atari was marketing these machines as really friendly, including the feature that there's one central expansion interface. Not only does everything hook up to the same place (well, unless you bought one of the non-SIO printers or modems) but you can hear the devices talking to the computer in a way that spotlights the SIO feature and makes you appreciate what's going on.
  8. The Atari could do completely silent loading, but the SIO cables have an unshielded audio-in wire so you'll always hear the serial data unless you make a better SIO cable or disconnect audio-in.
  9. Hey.. why's that Commodore monitor up so much higher?!?!?!!!
  10. Everyone wants to know why the 800 didn't have proper slots and that's pretty much the reason. Atari sold their products through consumer channels and they wanted to target the living room. This meant the 800 was a beast made of cast aluminum with shields on every removable surface. Exposed slots would never have passed, or would have added a lot of cost to make sure they couldn't leak. Then (thanks to the TI fiasco), the FCC relaxed their standards and computers could suddenly be sold wrapped in foil-lined cardboard. Bill, do you know how to get hold of the FCC standards from that time?
  11. Anyone can buy and bring home business machines. They just aren't guaranteed not to cause interference, and they cannot be designed to connect to the TV. I'm sure that people who bought the aftermarket modulator for the Apple had noisy picture issues. I'd love to know what the FCC docs from the late '70s say. There were probably other restrictions on how they were sold and marketed as well.
  12. This is one of the problems with NMOS technology. The power consumption is high and goes up with the number and speed of switching transistors. Atari's video was spread over 2 chips and most of the internals (everything not dealing with high-rez output) are switching at 3.58MHz. Vic II is one chip internally running at about 8MHz. That's asking a lot in a passively cooled plastic DIP package.
  13. Also remember that Apple didn't get their machines FCC certified for home use. This is how they got away with exposed ribbon cables. Everyone else had to devise a low-emission interface, and serial was it.
  14. The Apple drive card was very fast because it basically piped the raw drive signals to the computer's CPU. The downside was that without a traditional controller to shift in the data, the CPU was pretty much completely utilized during loading and the drives cables had to be fairly short for the drives to work reliably. It was a much cheaper solution than a dedicated microprocessor to serially feed the host machine, though.
  15. I don't remember the ingot being a problem back in the user group days. I thought it became an issue much later. Everything I heard about bad C64's was that in the early days many were bad from the box, so the issues got sorted before people started using them.
  16. Also, if a sound chip made years before SID can play a sawtooth, then isn't SID emulating Pokey?
  17. Emulate is a strong word. It basically implies something can be used in place of another thing. Pokey can't emulate SID. Pokey can make some of the same sounds as SID. SID can make some of the same sounds as Pokey. Playing a sawtooth is not emulation.
  18. I'm not sure I'd say Pokey can emulate SID. The CPU is doing most of the work. So, the A8 can emulate SID.
  19. As awesome as Pokey is, it's taken decades to figure out because it's main features are pretty basic, and then there's a bunch of neat things it'll do if you start trying everything. SID presented you with most of its tricks right up front. It was just a matter of applying your music skills. So even if you prefer Pokey, you have to realize that most programmers wouldn't have had the time to do more than the documentation suggested. And yes, they are both great sound chips.
  20. I've always had a question about the 6809 mod. According to the datasheets, there's a limit on how long you can halt the 6809 (probably due to dynamic cells) and a text badline exceeds that spec. Did I calculate something wrong or is just working anyway?
  21. I'd like to make a suggestion for the Hardware Manual regarding the Antic NMI bug (p. 56, Note 15). I don't believe this to be specifically an error on Atari's part. The earliest MOS manuals (MOS 1975, Synertek 1976) for the 6500 series state that NMI needs to be 2 cycles long and Antic's NMI is 2 cycles long. However, this is not sufficient when the 6502 is processing an IRQ and represents either a 6502 bug (that is, the designers thought 2 cycles was sufficient) or a documentation bug (that is, the datasheet author put in wrong information). Because the Antic spec complies with MOS's documentation, I suggest that this is a CPU/MOS bug more than an Antic one. What would make this an Antic bug is if the NMI's rise or fall was out of spec (which I don't know). The text is as follows: Page 38, Section 1.4.1.2.9, Paragraph 2. "The NMI signal must be low for at least two clock cycles for the interrupt to be recognized, whereupon new program count vectors are fetched." Later datasheets seem to be less detailed and don't give a minimum spec. I think it is usually assumed the program will reset the NMI hardware manually in the service routine. Since NMI's on the Atari occur at spaced intervals (400/800 reset is an exception), Atari decided to make them clear themselves according to the 2 cycle spec since they cannot happen back to back.
  22. Also, even though people discount the Atari's ~1.8MHz clock due to the 50% or so DMA losses during the screen, you have to remember that it was almost twice as a fast other 6502 machines during the blank which is arguably the best place to have it.
  23. To me, the best A8 games are the ones with graphics suited to the capabilities of the system. Things like Fort Apocalypse and Shadow World have a good high-contrast look. I know that with that big color palette it's tempting to waste all your colors on shading, but many of the later games just look too bland and monochrome because they tried to use extensive shading on everything.
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