
Shepardson Microsystems Pre-release Apple DOS Source Code - Notes
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* A single visual comparison of the bytes listed in the shepdos assembly listing
  and the bytes listed in the original pdf file listing has been performed, and
  they were found to be identical. That said, additional comparisons should be
  performed by a different set of eyes to help insure that the source file does
  indeed produce an identical binary as per the original source.
  
* The shepdos binary was tested by placing it on the appropriate sectors of a DOS
  3.1 master disk image and booting the result in an emulator. While it appeared
  to boot, and I could verify that DOS was relocated to where it needed to be in
  memory via the emulator debugger, all attempts to run any DOS commands just
  resulted in a "*** SYNTAX ERR" message.
  
  I've also assembled a complete RAWDOS binary based on the shepdos source and
  then used MASTER.CREATE to create a bootable disk image. Again the disk boots,
  but all DOS commands still resulted in a syntax error.

* The lowlevrw.asm source file contains the Apple DOS RWTS low-level subroutines
  written by Steve Wozniak and Randy Wigginton. The resulting assembly listing and
  binary are also included. This is the original source listing file posted on the
  CHM website and named "Apple_DOS_RW_30May1978.txt". Minor syntax changes were
  made to allow assembly with a cross-assembler.
  
  The resulting RWTS binary has been compared to sectors extracted from an Apple
  DOS 3.1 master disk, as well as the RAWDOS binary distributed with DOS 3.1, and
  somewhat surprisingly only a single byte was changed. The change occurs at binary
  offset 0x278, source line number 798. The delay byte in the original is $5F, and
  with DOS 3.1 it's $FF.
  
  Note that this source contains the RWTS low-level subroutines only, the RWTS main
  entry point routine (referenced as DISKIO in the shepdos source) has not been
  made available as of this writing.
  


  Scott LaBombard
  labomb@rochester.rr.com
  12/07/2013
  
  