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About ClausB

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    River Patroller

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    space and rocket history, astronomy, photography, math, computer programming, physics, digital electronics, Atari, aviation, sports cars, Star Trek, Star Wars, Doctor Who, my family, to name a few

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  1. I don't remember a second club but CHAOS later morphed into something else IIRC. At the founding meeting the president, being a Get Smart fan, suggested naming us Capitol Hill Atari Owners Society. Lansing is the capital of Michigan but there is no hill there and no one calls it Capitol Hill. Still the name stuck. It was a fun club!
  2. Fwiw I made some benchmark programs to test multiplication, trig and log functions a while back:
  3. The programmer can choose a lower res screen to balance CPU and DMA. Is that cheating or is it flexibility?
  4. Hardly. No matter what, the 6510 is limited to 1 MHz or less. In the A8 architecture, the programmer can choose between CPU dominance (up to 1.65 MHz) and DMA demands.
  5. Have you tried them without the switch box?
  6. We have Aldi here in Michigan. Which side are we on?
  7. Oh, I forgot about /OE. It acts just like another /CS, so you don't need the OR gate after all! Just connect /S7 to /CE and A12 to /OE. Edit: it would be simpler to leave pin 20 connected to /S7, and it would work, but the EPROM would draw more current that way, since it would become active internally whenever A12 is low, about half the time. Putting /S7 on pin 18 only activates it one eighth of the time.
  8. They are both needed but they both have to be low to select the ROM. They are both inputs to the ROM chip. The LS138 is not involved in ROM selection, it just happens that A12 goes there too.
  9. CS# connects to the /S7 output of the LS42, which decodes the 6502's 64K address space into 8 blocks of 8K each using A15, A14, and A13. /S7 is the highest block, addresses $E000 to $FFFF. But the OS ROMs are only 4K each so they need another address line to select one or the other, A12. When you include that signal, you decode the block $E000 to $EFFF, which is why they call A104 the E ROM. So CS connects to A12. You can replace the ROM chip with an EPROM if you add an OR gate between /S7 + A12 and the /CS input of the EPROM.
  10. A Teensy microcontroller which can be programmed to decode any key matrix and to act as a USB host. https://www.pjrc.com/teensy/td_keyboard.html
  11. I can't see which chips are on your perf board there, but I see 5 wires to the PIA, which implies the later, 16K bank mod. The earlier, 32K mod had only 3 wires.
  12. My dumper relocated the top 1K of the cart binary so that loading the file wouldn't overwrite the screen. The loader would then re-init the screen below the cart space, copy that 1K back up, and init the cart.
  13. BITD I built this cart extender with a switch to disable the ROM so that hot-plugging isn't needed:
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