11 Sector Disk Format

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11 Sector Disk Format

Postby bod/STAX » Sat May 10, 2014 1:41 pm

I'm not sure where I should post this question, so if it's in the wrong place can someone move it.

I was just wondering how safe is the 11 sector disk format?

My game is now using up all of an 820kb disk and I could really do with getting some more disk space
from somewhere whilst I need to keep what I have on one disk.

Do any games use this format? I think I know of one demo that uses this format (The YO! demo by TBC)

I've heard data can easily be corrupted using this disk format.
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Re: 11 Sector Disk Format

Postby exxos » Sat May 10, 2014 2:10 pm

I've always formatted at 11 sectors 83 tracks. Though buying "cheap" floppies at the time wasn't a good idea. I have heard mixed views on it over the years, some would never do it, some like me have always done it and never had any issues. Years ago I copied some 2,000 floppies over to my PC and there wasn't many unreadable ones.

Of course your floppy drive must support the extended formats. I would however recommend putting in a modern sony 1.44 drive (even if you do not use 1.44 stuff) as I have found older floppy drives getting somewhat unreliable in recent years. Or just put in one of my 1.44 kits and use HD floppies.
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Re: 11 Sector Disk Format

Postby troed » Sat May 10, 2014 3:39 pm

bod/STAX wrote:I was just wondering how safe is the 11 sector disk format?


My first demo (STar Demo, by ProWare Crew) was 83 or 84 tracks, 11 sectors. We _think_ people had problems copying it (I even believe one of the members of the group had an ST which simply couldn't write it out). I remember the only version of the demo that was available in any online archive was corrupted when I stumbled upon it a few years ago and I had to go search through our old backed up files to find another copy of the music that was missing.

However - it might've been more due to the extended number of tracks. I don't know.

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Re: 11 Sector Disk Format

Postby bod/STAX » Sat May 10, 2014 3:39 pm

OK Thanks.

I would have thought the STE's drive's wouldn't have much of an issue with this format as people
had been formatting to larger formats before the release of the STE.

Perhaps I'll just try it and see how I get on.
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Re: 11 Sector Disk Format

Postby AtariZoll » Sat May 10, 2014 4:21 pm

11 sectors/track was used by some commercial games. But it is not same as writing it on some Atari. Because copy machines can write it with higher density, so it is more reliable - may use bugger gaps. I don't recommend it.
Much better is to use some data packing. With good packer and fast depacking code (what may be really short - under 150 bytes) will have faster loadings too. While 11 sec/track loads pretty slow (interleave must be not 1). All in all 11 sect. format is slow and unreliable.
How good pack ratio can get depends from data, of course. I just made some packings with NRV2B algorythm (used in UPX for instance) - and it is really good, with very fast depacker. Should do some tests to see how well can pack your data.
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Re: 11 Sector Disk Format

Postby dlfrsilver » Sat May 10, 2014 7:19 pm

AtariZoll wrote:11 sectors/track was used by some commercial games. But it is not same as writing it on some Atari. Because copy machines can write it with higher density, so it is more reliable - may use bugger gaps. I don't recommend it.
Much better is to use some data packing. With good packer and fast depacking code (what may be really short - under 150 bytes) will have faster loadings too. While 11 sec/track loads pretty slow (interleave must be not 1). All in all 11 sect. format is slow and unreliable.
How good pack ratio can get depends from data, of course. I just made some packings with NRV2B algorythm (used in UPX for instance) - and it is really good, with very fast depacker. Should do some tests to see how well can pack your data.


If this was true, so why so many publishers used this format on atari ST. think about it, if the amiga can use 11 sectors per track format on basis, on double density disks, why the atari st could not ?

To me it's a false problem.
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Re: 11 Sector Disk Format

Postby bod/STAX » Sat May 10, 2014 8:54 pm

AtariZoll wrote:Much better is to use some data packing. With good packer and fast depacking code (what may be really short - under 150 bytes) will have faster loadings too. While 11 sec/track loads pretty slow (interleave must be not 1). All in all 11 sect. format is slow and unreliable.
How good pack ratio can get depends from data, of course. I just made some packings with NRV2B algorythm (used in UPX for instance) - and it is really good, with very fast depacker. Should do some tests to see how well can pack your data.


My game is already compressed heavily. I've even removed some of the larger chunks of code and created code generating routines to save disk space.
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Re: 11 Sector Disk Format

Postby calimero » Sat May 10, 2014 9:46 pm

dlfrsilver wrote:
AtariZoll wrote:11 sectors/track was used by some commercial games. But it is not same as writing it on some Atari. Because copy machines can write it with higher density, so it is more reliable - may use bugger gaps. I don't recommend it.
Much better is to use some data packing. With good packer and fast depacking code (what may be really short - under 150 bytes) will have faster loadings too. While 11 sec/track loads pretty slow (interleave must be not 1). All in all 11 sect. format is slow and unreliable.
How good pack ratio can get depends from data, of course. I just made some packings with NRV2B algorythm (used in UPX for instance) - and it is really good, with very fast depacker. Should do some tests to see how well can pack your data.


If this was true, so why so many publishers used this format on atari ST. think about it, if the amiga can use 11 sectors per track format on basis, on double density disks, why the atari st could not ?

To me it's a false problem.

read more carefully ;)

"11 sectors/track was used by some commercial games. But it is not same as writing it on some Atari. Because copy machines can write it with higher density, so it is more reliabl"
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Re: 11 Sector Disk Format

Postby simonsunnyboy » Sun May 11, 2014 9:29 am

I know that some drives handle them, other do not. It will work well for image only use with emulators and the .hfe but I would say, people using real floppies (those still exist) might get problems.

So what's wrong with a classic 80 2 10 format? Better ship a second disk and have reliable floppies than a single one that only 2/3 of the people can reliably use and copy.
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Re: 11 Sector Disk Format

Postby AtariZoll » Sun May 11, 2014 10:43 am

Yes, instead 11 sec./tr. I would go on 2 floppies.
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Re: 11 Sector Disk Format

Postby simonsunnyboy » Sun May 11, 2014 10:45 am

Not to mention, a lot of us will want to have a proper filed harddisk version anyway ;)
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Re: 11 Sector Disk Format

Postby Total Eclipse » Sun May 11, 2014 10:57 am

dlfrsilver wrote:If this was true, so why so many publishers used this format on atari ST. think about it, if the amiga can use 11 sectors per track format on basis, on double density disks, why the atari st could not ?

To me it's a false problem.


The Amiga didn't write at sector level. It would read an entire track in, look for a synchronisation string to signal the start of a track, and figure out the sector locations from there (so writing a single sector would actually involve a read and write of a whole track).

The advantage of this however was that there doesn't need to be any dead space between sectors to adjust for slightly different drive rotation speeds. There was just an amount of dead space at the end of each track worth of data. Therefore an 11 sector format is reliable and standard on the Amiga, but not necessarily so much on the Atari.
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Re: 11 Sector Disk Format

Postby IFW » Sun May 11, 2014 12:13 pm

Total Eclipse is right.
If you don't want to modify the sector data 11 sectors is safe, but you may want to use something like KryoFlux for duplication.
For any areas you would like modify (save, highscore) use a 9 or 10 sector format or a custom format instead.

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Re: 11 Sector Disk Format

Postby dlfrsilver » Sun May 11, 2014 3:17 pm

IFW wrote:Total Eclipse is right.
If you don't want to modify the sector data 11 sectors is safe, but you may want to use something like KryoFlux for duplication.
For any areas you would like modify (save, highscore) use a 9 or 10 sector format or a custom format instead.


ok :)
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Re: 11 Sector Disk Format

Postby MiggyMog » Sun May 11, 2014 5:23 pm

I have lost a few things over the years using 11 sector disk formats, they do seem to corrupt more easily. And Pc drives tended to hate them when trying to image them :-)

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Re: 11 Sector Disk Format

Postby bod/STAX » Sun May 11, 2014 6:32 pm

simonsunnyboy wrote:So what's wrong with a classic 80 2 10 format? Better ship a second disk and have reliable floppies than a single one that only 2/3 of the people can reliably use and copy.


I have all the games program code on one disk but I need to fit the first stage onto the same disk for the games "demo mode". It would look pretty lame to have to request the user to swap disks when demo mode is run. Also you wouldn't be able to run the game as a "shop window" game either this way.
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Re: 11 Sector Disk Format

Postby Zamuel_a » Sun May 11, 2014 8:46 pm

Can't you load everything from the 2 floppes to RAM first before you start the game? So that you would never ask for the person to insert the second disk. Or that the second disk is asked for before the game start and disk 1 is read to RAM.
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Re: 11 Sector Disk Format

Postby bod/STAX » Sun May 11, 2014 10:11 pm

The whole of the first disk could be loaded into RAM with no problem but the game would then only
work on a 4MB machine as opposed to 2MB.

The main game part itself uses just short of 1MB RAM and this is not including screen RAM (which
currently occupies 222KB).

I now have a version of the game running fine on an 82 track, 11 sector, 2 side disk with no problems
at all - just a little slow on loading.

*EDIT* - Actually thinking about it I suppose I could load the first stage's data into RAM before the title
screen load's the first time and then is used when needed. The first stage is only then reloaded if you
get past that stage. Then the demo mode would work without any disk swapping.
Last edited by bod/STAX on Mon May 12, 2014 6:40 am, edited 1 time in total.
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Re: 11 Sector Disk Format

Postby nativ » Sun May 11, 2014 11:00 pm

Zamuel_a wrote:Can't you load everything from the 2 floppes to RAM first before you start the game? So that you would never ask for the person to insert the second disk. Or that the second disk is asked for before the game start and disk 1 is read to RAM.


You could enable a memory detect and 'total load' if 4MB is found or have that option available in the menu, and saved with other preferences. I can appreciate having it initially set to only load the 1st level even on a 4MB machine if you just wanted a quick blast!
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Re: 11 Sector Disk Format

Postby bod/STAX » Mon May 12, 2014 6:43 am

I've been thinking about this overnight and I think all-being-well I'll go with the method I mentioned in the previous post.

One inconvenient disk swap at the very beginning is a minor thing if it means still having the game run how I want and
having enough disk space free on a reliable large disk format.

The 11 sector format could then only be used as an absolute last resort. The additional level data disk would either be
an 82 track, 10 sector, 2 sides format or the bog standard GEM format of 79 tracks, 9 sector, 2 sides (i think I've got
that right).
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Re: 11 Sector Disk Format

Postby AtariZoll » Mon May 12, 2014 7:43 am

Standard 720K floppy, so "GEM format" is 80 tracks - but because first track is 0 and not 1, last one is 79.
Looking forward to first (2 floppy) release :D
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Re: 11 Sector Disk Format

Postby IFW » Mon May 12, 2014 9:53 am

You are better off with the 11 sector format than using anything from track 80 - the issues come from modifying it, not reading it.
With 81+ tracks: some drives don't work with it and media is not guaranteed to work either.
Commercial games usually did not use more than 80 tracks to avoid possible compatibility issues.

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Re: 11 Sector Disk Format

Postby npomarede » Mon May 12, 2014 10:13 am

If you really need the capacity of 11*512 = 5632 bytes per track, I would suggest to use the format of 5*1024 + 1*512 ; that is, 6 sectors per track, but 5 sectors are 1024 bytes instead of 512.
This leaves more room for the GAPs and will be more reliable than pure 11 sectors per track (this format is used in the Union Demo and in many Rainbow Arts games for example).
It should be fairly standard to copy it with Fastcopy I think, larger sector should not be a problem, as the rest of the track will be standard and doesn't include protection.
But this requires your own disk loader, you won't be able to use the standard DOS directory structure with such format.

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