"UNKNOW'N FORMAT"

[Dbug]

Does anyone know how Sedoric determine what a valid format for a floppy is or not?
Right now when trying to use BACKUP with a non standard floppy (like Floppy Builder based), it will print the UNKNOW'N FORMAT error.
I was just wondering if we could somehow modify slightly the Floppy Builder format to embed the information like number of sectors, tracks, etc... so the normal DOS commands could be used to duplicate a disc for example.

Could it be as simple as for example having a minimal directory/fat sectors in the center of the disk geometry?

[Steve M]

Try asking Dr Ray. He's the most likely one to be able to answer.

[Ray030471]

BACKUP calls routine XPMAP for each referenced drive/disk. XMAP loads the first disk bitmap sector (track $14, sector $02) and checks to see if the first byte is $FF which indicates a SEDORIC formatted disk. This is not foolproof as any disk could have that byte in that location. However, if that byte in that disk location is not $FF then that disk does not have a SEDORIC format.
So, you could try and use NIBBLE to write the correct value, $FF, to the correct place in your Floppy Builder disk and see if BACKUP then works.

[Dbug]

Ok, so basically the floppy disk to have a bootable set of sectors at the start of the disk, and a valid "directory/fat" at the center of the disk.

I guess I could update FloppyBuilder to somehow allow reserving this sector 20/2 to be used to simulate Sedoric.

What would be the minimum data required to get DIR to work and report information indicating some stuff like a floppy name and maybe a single file that can show a short text like "This is a FloppyBuilder disk"?

[Chema]

That would be a nice touch! Good idea Dbug. I am not sure if that would be enough for backup to work, at least with usual sector sizes?

[Ray030471]

It might be better to create a bespoke (machine code) application, calling SEDORIC routines to read/write sectors, to do what you want rather than modifying your floppy builder disk.
I don't know anything about the floppy builder disk format and therefore cannot comment further.

[Dbug]

The format is not very complicated, it basically just has a couple sectors containing Oric DOS stuff to make the disk bootable, then the boot sector loads the loader into overlay and the loader knows where each file is located on disk (start track, sector and side, stored linearly).

The floppy itself is a standard 256 bytes sectors, 42 tracks with 17 or 18 sectors per track.

Losing one or two sectors to be able to use standard copy tools does not seem to be too bad of a deal to me

[Ray030471]

Yes, the fundamental disk format of floppy builder does lend itself to slight modification.

The relevant sectors are on track 20. The disk bitmap (FAT) is on sectors 2 & 3 and the actual directory (of files) starts at sector 4 (which can hold basic information for up to 15 files). Further directory sectors on that track would be 7, 10, 13 & 16, each being able to cater for up to 15 files.
Each file has a look-up table which requires at least one sector and then as many sectors as required to store the actual data.

However, as far as I can determine (look at the SEDORIC disassembly) BACKUP only requires that sector 2 on track 20 has the following contents
byte number value
$00 $FF
$06 number of tracks per side, eg $50 for 80-track disk
$07 number of sectors per track, eg $11 for 17 sectors per track
$09 bit 7 set for 2-sided disk otherwise 1-sided disk (usually $D0 for 2-sided, 80-track disk)

As far as I can see,t BACKUP doesn't check to see whether the target disk has the same number of sectors, tracks & sides (parameters) as the source disk but an error will occur if the target disk parameters are too small. However, choosing "Format TARGET disc (Y/N):" will sort this out.

I hope that this helps you to complete this task.

[Dbug]

However, as far as I can determine (look at the SEDORIC disassembly) BACKUP only requires that sector 2 on track 20 has the following contents
byte number value
$00 $FF
$06 number of tracks per side, eg $50 for 80-track disk
$07 number of sectors per track, eg $11 for 17 sectors per track
$09 bit 7 set for 2-sided disk otherwise 1-sided disk (usually $D0 for 2-sided, 80-track disk)

Thanks, I'll try to see if I can get something like that working
Is the rest of the sector described somewhere?

If I'm going to reserve a sector for that purpose, I could as well populate it properly

[Ray030471]

When I edit this, the message is nicely formatted but Preview and Post seems to strip many of the spaces. Therefore I have attached a PDF file of list below to make it easier to understand the information.

The "SEDORIC A NU" document might help with much of the details but here is a bit of help on the structure of sectors 2 & 3 of track $14 (all values in hexadecimal below where each XX represents a value between 00 & FF inclusively).

byte
number value purpose
00 FF to indicate a SEDORIC-formatted disk
01 00 unused but usually 00
02 - 03 XXXX number of free sectors on disk
04 - 05 XXXX number of files on disk
06 XX number of tracks per side, eg 50
07 XX number of sectors per track, eg 11
08 XX number of sectors making up DIR, at least 01
09 XX bit 7 is 0 for single-sided disk, 1 for double-sided disk, eg D0 which usually (but not necessarily) derives from the number of tracks per side
0A XX disk format type, eg 00 for Master, FF for slave - others are user-defined
0B - 0F 00 unused but usually 00
10 - FF XX disk bitmap (FAT), each byte here represents a unique set of 8 individual sectors - 00 means that all 8 sectors are allocated whereas,at the other extreme, FF means that all 8 sectors are free

The DIR (list of files with location information) is in sectors 04, 07, 0A, 0D, 10 of track 14 and then any free sector which is allocated dynamically to the DIR as required by SEDORIC. However, it looks like you don't need to consider this aspect. You probably don't need to concern yourself with sector 3 on track 14 either.

[Dbug]

Thanks, I'll try sometimes this week (right now I'm deep to the neck in non related things)

[Dbug]

So I did a quick test, and the DIR command now shows some corrupted data instead of ?UNKOWN'N FORMAT ERROR... and more importantly, the BACKUP command now does work just fine!

[Ray030471]

Super.

[Dbug]

And I wanted to attach that the other day, but then the forum died and did not accept the attachements!

The data added to the disk on track 20 sector 2

image_2025-10-06_202803375.png

And the result of DIR and BACKUP

image_2025-10-06_202608933.png