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Z80-MBC2_UCSDP

64K UCSD p-System IV.0 C/SBIOS V1.31 for Z80-MBC2 - (C) 2019 by GmEsoft

This is a custom bootstrap loader to load the Adaptable p-System IV for 8080/Z-80 on the Z80-MBC2 board.

The loader was initially designed to replace the autoboot.bin file on the SD card. It will mount one or more UCSD Pascal disk images, then load and execute the secondary bootstrap from the first disk image.

The bootloader can also be built as a bootloader for an additional disk set. In this case, the disk image files will need to be renamed from DS2Nxx.DSK to DSmNxx.DSK, with m = the disk set number. So, for the 4th disk set, the DSK names will begin from DS3N20.DSK.

Two disk images have been prepared for this system. They have been converted from the original 77-track 8 inch floppy disk images ; the link to the location from where the disk images is given below.

The new disk image format for the Z80-MBC2 board is of up to 77 tracks of 128 sectors, each of 128 bytes, for a maximum of 1.2 megabytes. The images are stored in files DSnNxx.DSK, with xx starting from 20 for the first disk. The disk set 'n' must be chosen from the config screen, so for the disk set number 2, we have to first activate CP/M 3.0 using the menu option 8: Change Disk set ; then select 4: Autoboot to load UCSD Pascal.

In the provided set:

  • DS2N20.DSK = disk 0 = SYS1: (loaded as unit #4);
  • DS2N21.DSK = disk 1 = SYS2: (loaded as unit #5);

Quick startup procedure:

  1. Copy the provided autoboot.bin file and the 2 disk images DS2N20.DSK and DS2N21.DSK to the root folder of the SD card.

  2. Start the Z80-MBC2 with the USER button pressed, to get the config menu.

  3. Select Disk Set 2 (CP/M 3.0) using the menu item 8: Change Disk Set.

  4. Choose boot mode 4: Autoboot.

  5. Enjoy UCSD Pascal.

Bootloader setup menu:

It is possible to configure some settings of the UCSD p-System before booting it. Those settings are stored in the last sector of the first disk's first track, track 0 512-byte sector 31, in the last 128- byte subsector (usually unused). Please note that the UCSD p-System works with 128-byte logical sectors, but the host Z80-MBC2 works using 512-byte physical sectors (FAT-32).

To access the setup menu, the USER button needs to be pressed while launching the p-System. Boot the system while holding the USER button down, keep the button down while pressing the number 3 (to boot the loader using the selected disk set) or 4 (to boot the custom AUTOBOOT.BIN file).

A screen like this one will appear:

64K UCSD p-System IV.0 C/SBIOS V1.3 for Z80-MBC2, Copyright (C) 2019 by GmEsoft
Build: Sep 05 2019 - 09:36:01

Scanning Volumes: [++++++++++++++++++++++++++++++++++++++++++++++++++]

Available volumes:
20:SYS1C     21:SYS2      22:INTERP    23:ADVX      24:ADVSRC    25:SYSCPM1
26:STARTUP   27:UTIL1     28:ASM1      29:STARTRK   30:GAMES     31:KBDB
32:KBDBX     33:88SYS     34:88SYS     35:SYSCPM1   36:Z8SYS     37:INTCPM
38:INTZ80    39:STARTUP   40:SYS1      41:STARTUP   42:SYS1      43:SYS3
44:SYSCPM1   45:UTIL1     46:UTIL1     48:ASM1      50:SYS1S     51:PASCAL1
80:88SYS     81:ASM1      82:ASM2      83:ASM3      84:INTCPM    85:STARTUP
86:SYS1      87:SYS2      88:SYS3      89:SYSCPM1   90:UTIL1     91:UTIL2


Select volume numbers (<T>ens, <U>nits, <ret> to accept):
#04 20:SYS1C   ?
#05 21:SYS2    ?
#09 51:PASCAL1 ?
#10 23:ADVX    ?
#11 24:ADVSRC  ?
#12 22:INTERP  ?

Select BIOS Type (<S>BIOS, <C>BIOS, <ret> to accept):CBIOS?

The configurable settings are:

  • the mapping of 6 logical UCSD p-System 'block' units (#4-#5, #9-#12) to 6 physical disk image files DSn0xx.DSK: the value of n is fixed, it is the disk set number; the value of xx is in the range 00-99;

  • the type of BIOS: CBIOS and SBIOS: CBIOS must be selected if the boot disk image is CP/M Adaptive System and SBIOS must be selected if the boot disk image is Full Adaptive System. The jump vectors and the registers used to exchange parameters between the system and the BIOS routines are different and incompatible (more info later about this).

How to create the set of disks ?

1: Download the original disk image from the web. I chose to download them from the Z80-SIM page at ClassicCmp.org, at this URL: http://www.classiccmp.org/cpmarchives/cpm/mirrors/www.unix4fun.org/z80pack/ftp/ucsd-iv.tgz

2: Extract the 2 disk images from the archive: ucsd-iv-1.dsk and ucsd-iv-2.dsk.

3: Convert the disk images to the Z80-MBC2 format using the provided tool makedisk (source code: makedisk.c):

makedisk -M:DS2N20.DSK -I:ucsd-iv-1.dsk -L:128 -SI:26 -SO:128 -F:T0 -T:T1 -D:T0 -F:T1 -T:T77 -D:T1 -P:T77
makedisk -M:DS2N21.DSK -I:ucsd-iv-2.dsk -L:128 -SI:26 -SO:128 -F:T0 -T:T1 -D:T0 -F:T1 -T:T77 -D:T1 -P:T77

This will extract the first 26-sector track of the source images and copy the sectors to the first 128-sector track of the new disk images. Then data from the tracks 2 to 77 from the source images to the new images starting from track 2, adjusting for the new track size. Finally the images will be padded for the 1.2 megabytes capacity.

The syntax for makedisk is:

Makedisk -M:outfile [-L:lrl] [-SI:input track size] [-SO:output track size]    
         [ [-I:infile] [-XI:input interleave] [-KI:input skew]
           -F:[T]from -T:[T]to -D:[T]dest ... ]
         [ -P:[T]padsize ]
             T for whole tracks, else sectors
Defaults:
         -L:128   bytes per sector
         -SI:26   sectors per side for input (8inch format)
         -SO:128  sectors per side for output (Z80-MBC2 image format)
         -XI:1    (no interleave)
         -KI:0    (no skew)

4: Start the UCSP p-System.

5: Set today's date using F(iler - D(ate.

Example: 24-Aug-19

6: Extend the disk size of units #4 and #5 using X(ecute - SYS2:DISKSIZE:

Change directory size of what unit? (4,5,9..12) --> 4, then 5

What is the new directory size in 512 byte blocks ? --> 2432(=76*32)

7: Configure the p-System to the characteristics of the UTERM terminal (30 lines of 80 characters), so the scrolling in the editor will perform correctly, using X(ecute - SETUP:

SETUP: C(hange T(each H(elp Q(uit --> C
CHANGE: S(ingle) P(rompted) ... --> P
--> reply N until getting FIELD NAME = SCREEN HEIGHT, then reply Y
NEW VALUE: --> 30
Then reply N to the remaining prompts.
Type L to check that the new value has been accepted.
--> Q(uit) to exit change mode
--> Q(uit) to save new settings --> D(isk), then E(xit)

The new settings are now saved to SYS1:NEW.MISCINFO. Rename this file to SYS1:SYSTEM.MISCINFO, overwriting the existing file, using F(iler - C(hng:

Change what file ? --> NEW.MISCINFO
Change to what ? --> SYSTEM.MISCINFO
Remove old SYS1:SYSTEM.MISCINFO ? --> Y

8: Alter the GOTOXY procedure, to make it accept row numbers between 1 and 30.

F(iler - G(et the workfile --> gotoxy
Q(uit the Filer
E(dit
Change line 13 to read:
    IF Y>29 THEN Y:=29;
(go over the 3; D(let, press the spacebar once then Ctrl-Z; I(nsrt, hit 9 then Ctrl-Z)
Q)uit the editor and U)pdate the workfile
C)ompile the file
F)iler - S)ave
Save as SYS1:GOTOXY ? --> Y
Q)uit the Filer

Then bind GOTOXY into the system library:

X)exute --> SYS2:LIBRARY
Output file? --> NEW.PASCAL
Input file? --> GOTOXY
--> T(ext (Interface sections will not be copied)
--> 0
From slot #? 0 --> spacebar
To slot #? --> 16
--> N(ew
Input file? --> SYSTEM.PASCAL
--> E(very (get all slots except GOTOXY)
--> Q(uit LIBRARY

Now using F)iler rename NEW.PASCAL to SYSTEM.PASCAL:

--> F)iler - C)hng
Change what file ? --> NEW.PASCAL
Change to what ? --> SYSTEM.PASCAL
Remove old SYS1:SYSTEM.PASCAL ? --> Y
--> K)rnch to compress the directory
Crunch what vol ? --> :
From end of disk, block 2432  ? (Y/N) --> Y

Reboot the system. The p-System should now use all 30 UTERM's lines.

How to build the bootloader ?

1: Download the ZMAC assembler from here (or use getzmac.sh): http://48k.ca/zmac.html

2: Execute MAKEIT.BAT. This will create the file autoboot.bin that will be copied to the SD card.