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Re: [cosmacelf] Re: Parallelf

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  • Lee Hart
    ... Well, I don t know about that... NASA used 1802 s in spacecraft, and usually had a bunch of them rather than just one. The groups provided redundancy to
    Message 1 of 35 , Apr 15 1:48 PM
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      On 4/15/2011 10:58 AM, Richard wrote:
      > Microcontrollers are nice and well, I will even have to use a simple
      > one for the PS/2 port. The nostalgia value also is a point. When I
      > call it Elf, then there must be Elf inside :)
      >
      > Microcontrollers would also be in the way for some ideas. Supposed we
      > had some interface with which we could upload data, commands to each
      > CPU card and download results, then I would also like to use the
      > interface to upload executable code. This way the other CPUs could
      > still be put to work, even when they are not needed for their
      > particular purpose at the moment. Then it will be practical when all
      > CPUs agree on one machine code.
      >
      > Also, something like an operating system would be distributed among
      > the CPU cards, including the protocol for the interface. For this it
      > would again be nice to program in one machine code and not in
      > several.
      >
      "johngodsey@" wrote:
      >> This reminds me of what the folks on the Parallax forums do with
      >> the Propeller. For extra processors attached to the 1802 why not
      >> use microcontrollers? Some of them can do video pretty well
      >> although it would take away from the nostalgia value.

      Well, I don't know about that... NASA used 1802's in spacecraft, and
      usually had a bunch of them rather than just one. The groups provided
      redundancy to improve reliability, and also allowed parallel processing
      for speed.

      The 1802 has 8 clock cycles for each bus cycle. All signals are latched
      at one of the 8 edges in each clock cycle; the data does not have be
      valid for the entire 8 cycles.

      This allows up to eight 1802's to be multiplexed to the same memory. The
      memory just needs a fast enough access time to respond in one clock
      cycle time (easy with modern memory chips).

      Simple example: Two 1802's running on the same clock frequency, but with
      their bus cycles 4 clocks out of phase. A multiplexer switches the
      memory's address and data back and forth between the two.

      Communications between the 1802's would be by flags in the shared
      memory. The 1802's could be running independent programs, or separate
      threads in one main program. FORTH would be one example of a language
      that already supports such threading.
      --
      Lee A. Hart | Ring the bells that still can ring
      814 8th Ave N | Forget the perfect offering
      Sartell MN 56377 | There is a crack in everything
      leeahart earthlink.net | That's how the light gets in -- Leonard Cohen
    • Richard
      Thanks. That was a bit hasty. It s on the list for the next changes. I will probably get home from work earlier tomorrow and then have a little more time.
      Message 35 of 35 , May 11, 2011
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        Thanks. That was a bit hasty. It's on the list for the next changes. I will probably get home from work earlier tomorrow and then have a little more time.
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