RomWBW/Source/pSys/ReadMe.txt

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