ADL disk file format.

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Prime
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ADL disk file format.

Post by Prime » Fri Nov 02, 2018 10:38 pm

Hi all,

In trying to get FlashFloppy working with my Nascom, Mark H pointed out that it uses identical disk geometry to the L format ADFS disks namely :

80 tracks of 16, 256 byte sectors, double sided.

So I got a nascom image and renamed it .ADL, and put it in one of my Goteks, great doing a ]D brings up the disk catalog. However trying to load files off the disk fails :(

So by default are .ADL files track or side ordered within the file, I suspect that I need the disk to be track ordered namely :

offset head track
0 0 0
TS*1 1 0
TS*2 0 1
TS*3 1 1

etc where TS= track size namely 16*256.

Is this how ADL disks are layed out?

Cheers.

Phill.

Coeus
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Re: ADL disk file format.

Post by Coeus » Fri Nov 02, 2018 10:47 pm

From the few examples I have to hand, i.e. the Master welcome disc and the ARM evaluation system disc set these appear to be interleaved sides, i.e:
  • head 0, track 0
  • head 1, track 0
  • head 0 track 1
  • head 1 track 1
etc.
Last edited by Coeus on Fri Nov 02, 2018 10:47 pm, edited 1 time in total.

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yellowpig
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Re: ADL disk file format.

Post by yellowpig » Thu Nov 08, 2018 8:08 pm

There are some details about this on my website at: http://www.cowsarenotpurple.co.uk/bbcco ... /adfs.html

Some of the stuff on that page is elementary, but it is followed by some technical detail.

A couple of points you may like to note:

(a) All the tracks on side 0 are followed by all the tracks on side 1.

(b) The files in a directory have to be in alphabetical order. If a file is out-of-order then only files up to that point will be recognised. (ADFS has its own (slightly eccentric) way of ordering file names that include non-alphanumeric characters - I would never recommend using such.

David

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Re: ADL disk file format.

Post by Coeus » Fri Nov 09, 2018 1:57 am

yellowpig wrote:
Thu Nov 08, 2018 8:08 pm
(a) All the tracks on side 0 are followed by all the tracks on side 1.
That contradicts your own website which says, in the section "Notes about Disk Images and Emulators":
One thing to notice about this is that *.dsd and *.adl files store sectors in the increment order sector - track - side. So track 0:side 0 is followed by track 0:side 1 then track 1:side 0 etc.

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yellowpig
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Re: ADL disk file format.

Post by yellowpig » Fri Nov 09, 2018 8:57 am

Yes. You are right. I was thinking about physical disks and had forgotten that we were talking about images.

Sectors are stored in a different order on physical disks from the way they are stored in (.adl) images. If you consider all the secotors in their logical order, then on a (large) physical ADFS disk the first 1280 sectors fill the first side, and the later sectors then fill the second side. adl images, on the other hand, take this physical structure and interleave the tracks on the two sides.

What this actually means is that in a .adl image the logical sectors appear in the order:
0 1 ... 15 1280 1281 ... 1295 16 17 ... 31 1296 ...

If you are going to work with .adl images, you have to re-order the data before and after manipulating it.

David

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