This directory contains a port of p-System IV.0 for RomWBW.

It was derived from the p-System Adaptable Z80 System.  Unlike
some other distributions, this implements a native p-System
Z80 BIOS, it does not use a CP/M BIOS layer.

Files:

loader.asm     p-System primary loader for RomWBW
bios.asm       p-System BIOS for RomWBW HBIOS source (TASM)
biostest.dat   binary image of SBIOSTESTER
boot.dat       binary image of p-System bootstrap
psys.vol       first (boot) slice, all p-System dist files
blank.vol      a generic blank p-System volume
fill.dat       used to complete the track 0 build (see below)

Notes:

This adatation runs on a single RomWBWW HBIOS hard disk
type device (CF Cart, SD Card, IDE drive, etc.).  The
image built (psys.img) should be copied to your disk media
start at the first sector.  You can then boot by selecting
the corresponding disk device unit number from the RomWBW
boot loader prompt.  The p-System disk image (psys.img) is
entirely different from the RomWBW CP/M-style disk images.

The boot device hard disk is broken up into 6 logical
p-System volumes.  These are referred to as p-System
slices.  A single RomWBW disk device can contain either
CP/M-style slices or p-System slices, but not both.
Each p-System slices is exactly 8 MB and support for
exactly 6 slices is provided.

The first track of each volume contains all of the code
required to boot the p-System.  However, the assignment
of the volumes is always in the order that the slices
appear physically on the hard disk device.  Normally,
you would just boot to slice 0 from the RomWBW Boot
Loader.

The first track contains the following:
 - 4 sector p-System primary loader for RomWBW HBIOS
 - 1 sector p-System BIOS for RomWBW HBIOS
 - 4 sector p-System bootstrap
 - 7 sector filler to complete a full track

The p-System bootstrap is a binary image provided in the
p-System distribution.  The loader and the BIOS are
custom for RomWBW and the source is provided here.

The layout of the first track does not conform exactly to
the recommended p-System layout.  The recommended layout
is not possible because it conflicts with the RomWBW
definition for a boot track.  However, the changes are
simply slilghtly different sector assignments for the
different boot componets -- the general boot sequence
and mechanism for the p-System is completely standard.

The logical disk geometry used by this p-System
adaptation is:
 - 512 byte sector length
 - 16 sectors per track
 - 192 tracks per disk

This layout does not occupy the full 8MB slice size
allocated.  This is to allow for future expansion of
the filesystems.

The p-System distribution includes a BIOS tester that
is provided as a binary image.  This tester was used
to test the BIOS code in this adaptation.  Note that
the tester fails for the BIOS as is.  After a lot of
code tracing, a definite bug was identified in the
tester that exists for 512 byte sectors (which are
supported).  When the BIOS is modified to use 128 or
256 byte sectors, the tester completes perfectly.
Significant use of the BIOS shows there are no issues
for a normal running system with 512 byte sectors.

The boot disk provided here was constructed by simply
copying all of the content from the p-System distribution
disks onto the boot disk.  SYSTEM.MISCINFO was updated
for an ANSI terminal.  The GOTOXY routine in
SYSTEM.PASCAL was also updated for an ANSI terminal.
Note that the BIOS conwrit routine is hacked to add
a '[' to any output escape character.  This is needed
because p-System has limited terminal escape sequence
handling configuration.

At this time, there is no straightforward way to move
files in and out of the p-System volumes.  There are
ways to do this, but they are complicated.  Please
contact me if you are interested.

There is currently no support for floppy drives.

Wayne Warthen
wwarthen@gmail.com

3:13 PM Thursday, January 12, 2023