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 Extended 

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.asm       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

 - 1.5 sector p-System BIOS for RomWBW HBIOS

 - 4 sector p-System bootstrap

 - 6.5 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 only slightly 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.  It turns out that this code has a blatant error that

causes it to fail for 512 byte sector sizes (which are allowed).

To resolve this, biostest.dat was disassembled and patched to correct

the error.  The original version is retained as biostest.old.



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 a very limited terminal 

escape sequence handling configuration.  The debugger code as added to 

SYSTEM.PASCAL to enable the debug function.  SYSTEM.INTERP was modified 

to enable the extended BIOS functions.



The build/makefile creates the psys disk image (psys.img) by adding 

concatentating psys.vol and blank.vol (after adding track 0 contents to 

each).  psys.vol and blank.vol are recognized by CiderPress and 

CiderPress can be used to add/remove files from these volumes.  

However, there is currently no straightforward way to extract the 

volumes from the disk image.  If you are good with a binary disk 

editor, you can do it that way.  Please contact me if you are 

interested in pursuing that.



There is currently no support for floppy drives.



Wayne Warthen

wwarthen@gmail.com



5:42 PM Sunday, January 15, 2023