Question about root block differences in UFO Uknown disks

[FrodeSolheim]

I reported UFO - Enemy Unknown (1994)(MicroProse)(AGA)(M3)(Disk 1 of 4)[cr Bad Karma].adf in the TOSEC renaming thread, and decided to look at disks 2, 3 and 4, and compared the [a] variants to non-[a]

This is the result for Disk 4 (disk 2 and disk 3 comparisons were likewise).

i see that the [a] disks have bm_flag == VALID (-1, ff ff ff ff), while the non-[a] disks have the value 1 (??) Is this symptomatic of a faulty copy program?

While the disks may both work fine (how does AmigaDOS treat disks with bm_flag == 1?), is this a reason to prefer the [a] over the other?

The other byte differences in the root blocks are only dates (and root block checksum of course).

Another peculiarity is that the root block pointer in block 0 is 0, not 880 (this is for all disks 2, 3, and 4, both [a] and non-[a]).

ADF File Compare
================
A: DOS disk, FFS
   UFO - Enemy Unknown (1994)(MicroProse)(AGA)(M3)(Disk 4 of 4)[cr Bad Karma].adf
B: DOS disk, FFS
   UFO - Enemy Unknown (1994)(MicroProse)(AGA)(M3)(Disk 4 of 4)[cr Bad Karma][a].adf

WARNINGS FOR DISK A
===================
WARNING: Root block is at position 0, not 880
WARNING: Trying 880 anyway...
WARNING: bm_flag != 0xffffffff

WARNINGS FOR DISK B
===================
WARNING: Root block is at position 0, not 880
WARNING: Trying 880 anyway...

FILE LIST
=========
(the disks have the exact same files and file contents)

BLOCK COMPARISON
================

block 880 differ:
 - A - used
 - A - root block
 - B - used
 - B - root block

    offset 010     00 00 00 00 6a 45 d2 5a     00 00 00 00 6a 45 a9 04 
    offset 138     00 00 00 01 00 00 03 71     ff ff ff ff 00 00 03 71 
    offset 1a0     00 00 00 00 00 00 01 00     00 00 00 00 00 00 17 d2 
    offset 1a8     00 00 04 8b 00 00 03 21     00 00 03 81 00 00 02 05 
    offset 1e0     00 00 0b 92 00 00 01 00     00 00 0b 92 00 00 17 d2 
    offset 1e8     00 00 04 8b 00 00 03 21     00 00 03 81 00 00 02 05

Anyone have any words of wisdom?

[Galahad/FLT]

What is the DOS header in hex for the boot block track? Should be "DOS",x, x=number

[FrodeSolheim]

Originally Posted by Galahad/FLT

What is the DOS header in hex for the boot block track? Should be "DOS",x, x=number

44 4F 53 01 00 00 00 00 00 00 00 00

I don't know that anything's wrong with it, but I've been using http://lclevy.free.fr/adflib/adf_info.html, and it does not seem to simply that the root block pointer is optional - which is why I wondered about this. Perhaps AmigaOS assumes the default (880) if this value is 0, or that it was never really used?

EDIT: Actually, the ADF FAQ seems to contradict itself, another place it says that a Minimal blank floppy disk first block looks like this (so root block pointer will be 0 in this case):
0 char 4 ID 'D''O''S' + flags (0 -> 5)
4 long 1023 full of zeros

[Toni Wilen]

Root block value in boot block is completely unused. Many adf images have garbage there. (aros did use it for a while but it broke many disk images..)

Bitmap valid field is DOS boolean, DOS uses 0 and -1 (DOSFALSE and DOSTRUE) when writing, usually (there may be exceptions) any non-zero value works in place of -1.

Possibly it has been validated or optimized or something by some 3rd party program?

[FrodeSolheim]

Originally Posted by Toni Wilen

Root block value in boot block is completely unused. Many adf images have garbage there. (aros did use it for a while but it broke many disk images..)

Thanks, I suspected this was the case...

Originally Posted by Toni Wilen

Bitmap valid field is DOS boolean, DOS uses 0 and -1 (DOSFALSE and DOSTRUE) when writing, usually (there may be exceptions) any non-zero value works in place of -1.

Possibly it has been validated or optimized or something by some 3rd party program?

Ah, thanks for clarifying, really appreciated

And yes, the bitmap valid field was 1, so not just any random garbage value. I suppose this could indicate a particular copy program has been used, one which simply uses 1 for valid (or true, generally) and 0 for false... -I assume -1 would written by most copiers...

I'll try to get this additional information added to the ADF FAQ