Herb Johnson Dec 2016

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I looked at the Morrow DJ2D disk I have, using "DU", the CP/M disk sector editor. Even though my Z-100 CP/M-85 system doesn't support the Morrow double density format, I was able to attempt to copy the boot tracks.



I discovered that track 00 is single density; but track 01 is double density, it has more than 26 sectors of 128 bytes. So using CP/M "sysgen" to read and write single-density tracks, only copied track 0 and about half of track 1, to another CP/M single-density disk.



 Not enough....but in principle you might be able to use this single-density disk, for testing, it should load at least track 0 into memory. It may flunk on track 1 as it's the wrong density...





And I did inspect the sectors. I took photos of the hex dumps.



Track 0 sector 1 has the first of a number of "boot sector loaders", just like the manual suggests. There's different loaders for different disk geometries. I looked at the BIOS sectors to identify the BIOS: "24K CP?M ver 3.3 Cbios rev 3.2 for Tinker toys Diks Jockey 2D Controller @ E000H"  So this Morrow disk is the right disk for your controller.



The BIOS addresses on this disk, are



C3 A0 53

C3 fC 53

C3 40 56

Cd 4c 56



....and so on. So that tells you, BIOS is located at 5300H and up. That's informative. BIOS is on track 1, "sector 35" which is actually some physical double-density sector.



the first boot sector has this dump



3180E73E 063C3CFE 1BCA0042 DA11E7D6

13320437 4FCD0FE0 21004111 0001197C

FE46DA31 E7C22EE7 7DFE80DA 32E71180

F6192219 E7444DCD 12E00100 0AC5CD0C

E0CD15E0 C1D203E7 05C23DE7 C32AE000

ALL ZEROS...



translation

 org 0e700H



 lxi sp, 0e780h

 mvi a, 06h

 inr a

 inr a

 cpi 1bh

 jz 4200h

 jc 0e711h

 sui 13h

 sta 3704h

 mov c,a

 call 0e00fh

 lxi h, 4100h

 lxi d,0100h

 dad d

 mov a,h

 cpi 46h

 jc 0e731h

 jnz 0e72eh

 mov a,l

 cpi 80h

 jc 0e732h

 lxi d,0f680h

 dad d

 shld 0e719h

 mov b,h

 mov c,l

 call 0e012h

 lxi b,0a00h

 push b

 call 0E00ch

 call 0e015h

 pop b

 jnc 0e703h

 dcr b

 jnz 0e73dh

 jmp 0e02ah

 nop

 nop

 nop



 end











   e700                  org 0e700H



   e700   31 80 e7       lxi sp, 0e780h

   e703   3e 06          mvi a, 06h

   e705   3c             inr a

   e706   3c             inr a

   e707   fe 1b          cpi 1bh

   e709   ca 00 42       jz 4200h

   e70c   da 11 e7       jc 0e711h

   e70f   d6 13          sui 13h

   e711   32 04 37       sta 3704h

   e714   4f             mov c,a

   e715   cd 0f e0       call 0e00fh

   e718   21 00 41       lxi h, 4100h

   e71b   11 00 01       lxi d,0100h

   e71e   19             dad d

   e71f   7c             mov a,h

   e720   fe 46          cpi 46h

   e722   da 31 e7       jc 0e731h

   e725   c2 2e e7       jnz 0e72eh

   e728   7d             mov a,l

   e729   fe 80          cpi 80h

   e72b   da 32 e7       jc 0e732h

   e72e   11 80 f6       lxi d,0f680h

   e731   19             dad d

   e732   22 19 e7       shld 0e719h

   e735   44             mov b,h

   e736   4d             mov c,l

   e737   cd 12 e0       call 0e012h

   e73a   01 00 0a       lxi b,0a00h

   e73d   c5             push b

   e73e   cd 0c e0       call 0E00ch

   e741   cd 15 e0       call 0e015h

   e744   c1             pop b

   e745   d2 03 e7       jnc 0e703h

   e748   05             dcr b

   e749   c2 3d e7       jnz 0e73dh

   e74c   c3 2a e0       jmp 0e02ah

   e74f   00             nop

   e750   00             nop

   e751   00             nop



   e752                  end





This is not in the manual....but clearly it runs at e700h, and it loads something into 4100H and up... tricky selfmodifying code there...





herb