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Ideas for Network Boot of Radio Shack Color Computers

Radio Shack Color Computers

Coco1: 1980: 4K or 16K

Coco2: 1983: 64K

Coco3: 1986: 128K or 512K (with Memory Mapping Unit)

The 6809 CPU sees only a 64K memory space.

Typically 32K for RAM and 32K for ROM:

$0000 - $7FFF RAM
$8000 - $9FFF Extended Color Basic
$A000 - $BFFF Color Basic
$C000 - $DFFF Cartridge 8K ROM (possibly Disk Basic)
$E000 - $FDFF Another 8K ROM (possibly Super Basic(?))

$FE00 - $FEFF Trampoline RAM
$FF00 - $FFFF Device I/O


What will fit in 8K Cartridge Rom (on an Ethernet card)?

Write in ASM? C? FORTH?

  • DHCP for network addresses
  • or STATIC address assignment?
  • Unique ID per ROM (hostname for DHCP, Ethernet MAC)
  • Quickly load the next chunk of code from TFTP
  • Load bare metal programs
  • Load other operating systems (NitrOS-9, Flex, Ya-dos, Fuzix)
  • Debugging Monitor (view memory, registers, run code)
  • OpenFirmware-ish interpreter (better debugging!)
  • What would a new "network operating system" look like? ( videotex? chromebook? )
  • Easter Eggs (simple built-in game? image? screen saver?)


    Compiled ROM code sizes so far, in bytes, for one test program:



    8413 :: cmoc -O0
    7951 :: cmoc -O1
    7040 :: cmoc -O2
    7258 :: gcc -O0
    5209 :: gcc -O1
    5598 :: gcc -O2
    5021 :: gcc -Os
    5450 :: gcc -O2 -fomit-frame-pointer
    4855 :: gcc -Os -fomit-frame-pointer
    4767 :: gcc -O2 -fwhole-program
    4690 :: gcc -O2 -fomit-frame-pointer -fwhole-program
    4389 :: gcc -Os -fwhole-program
    4288 :: gcc -Os -fomit-frame-pointer -fwhole-program

    Other problems: gcc for 6809 has bugs in some of these modes.

  • boot_lemma.bak
  • boot_lemma.bak


    https://go.dev/doc/code (how to write Go code)

    https://www.mikrocontroller.net/attachment/1483/SPI_74HC595.pdf ( bidir SPI with -165 and -595 ) ( cache: /file SPI_74HC595.pdf )

    level shifter: https://www.adafruit.com/product/735

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