On Superfloppies and their Images

[rloew]

DOS and Windows do not seem to care what the Partition Type Code is, if in the allowed range, when determining Filesystem Type.

Sure they do not, as the DOS and Windows we are currently using were all made AFTER the "invention" of types 04, 06 and 0C, this is IMHO the same "side effect" as the "large Sectors vs. Small Sectors".

If you try:

1. DOS <3.3
   
2. DOS 3.3
   
3. DOS 4.0
   
4. DOS <=6.22
   
5. DOS >= 7.0
   

on a set of 01/04/06/0C partitions, your mileage should (and will) vary

I think that in common language we could consider:

• FAT12 an ancestor of FAT16
  
• FAT16 04 a sub-set of FAT 06
  
• FAT 16 06 a sub-set of FAT 0C
  

Then draw a line around 1995 and say that everything coded after is accessing *any* of the above in the same way (which allows for some of the tricks we are discussing).

As I see it, trying dencorso'S image in DOS 3.3 should fail, as that version of Dos should know nothing about "Large sectors".

jaclaz

Of course I was referring to the later DOS Versions. The early ones had many limitations.

DOS 3.3 would be limited to 32MB.

Superfloppies and CD Floppy Emulations do not use Partition Codes, so that issue does not apply.

The Partition Type for the LBA version of FAT16 is 0x0E not 0x0C. Type 0x0C is the LBA Version of FAT32.

[jaclaz]

The Partition Type for the LBA version of FAT16 is 0x0E not 0x0C. Type 0x0C is the LBA Version of FAT32.

Yes, my bad corrected in previous post(s))

jaclaz

[dencorso]

Well, since the 100 MB image works OK in a real Zip100, I think the next step would be to create a bootable FAT-12 128 MB SD card and boot from it, for us to have an air-tight proof-of-concept that the real limit of FAT-12 is 128 MB. This may take some time, because 128 MB are not findable around here anymore... I'm going to get a good one, preferably a SanDisk or a Transcend from eBay. When I get it, I'll post my results. Would Bart PE or LiveXP boot from FAT-12? Can the FAT-16 NT boot sector be coerced to work with FAT-12? Seeing how FAT-12 and FAT-16 share code, I bet it would. What do you all think about it?

[rloew]

Well, since the 100 MB image works OK in a real Zip100, I think the next step would be to create a bootable FAT-12 128 MB SD card and boot from it, for us to have an air-tight proof-of-concept that the real limit of FAT-12 is 128 MB. This may take some time, because 128 MB are not findable around here anymore... I'm going to get a good one, preferably a SanDisk or a Transcend from eBay. When I get it, I'll post my results. Would Bart PE or LiveXP boot from FAT-12? Can the FAT-16 NT boot sector be coerced to work with FAT-12? Seeing how FAT-12 and FAT-16 share code, I bet it would. What do you all think about it?

You can always create a smaller Partition than the Device size, or use a Hard Disk Partition for proof of concept.

Non-Bootable Partitions can be as much as 256MB without Patching DOS, although some utilities don't work.

The NT Boot Sector may be modifiable to support FAT12 but I suspect that NTLDR will not work

[dencorso]

The NT Boot Sector may be modifiable to support FAT12 but I suspect that NTLDR will not work.

Well, that's a can-of-worms I'm saving for later.

I can always hope NTLDR will work, until proven wrong by a test.

But first we must know whether the boot sector will find NTLDR, to give it a chance to work (or fail)...

[jaclaz]

The NT Boot Sector may be modifiable to support FAT12 but I suspect that NTLDR will not work.

Well, that's a can-of-worms I'm saving for later.

I can always hope NTLDR will work, until proven wrong by a test.

But first we must know whether the boot sector will find NTLDR, to give it a chance to work (or fail)...

Why it shouldn't work?

I mean NTLDR does work on a "normal" FAT12 floppy, I don't see any "normal" reason why the bootsector shouldn't find NTLDR.

Making NTLDR based floppies to boot machines with a corrupted NTLDR or BOOT.INI is (was) a normal task:

http://support.microsoft.com/kb/305595/en-us

http://www.xxcopy.com/xxcopy33.htm

jaclaz

[dencorso]

Well... since we've agreed that a filesystem is a bunch of bytes (or whatever) that can be divided in a System Area and a Data Area (we did agree to that, didn't we?), I'm thinking that there's one more concept I'd like to find a common terminology for:

(i) By looking at the floppy disk format list I posted, we can easily see that the maximum a common "1.44 MB" FDD can actually format is a 83 * 21 * 2 * 512 floppy, which means 1,784,832 bytes or 1.70 MiB (before adding the filesystem), the so called "1.74 MB" floppy.

(ii) The "2.88 MB" floppy uses a special FDD, which can create twice the sectors the normal one can.

So I conclude that the most extreme floopy format possible (although I've never heard about anyone ever having formatted a floppy like this) should be a 83 * 42 * 2 * 512 floppy, which means 3569664 bytes or 3.40 MiB (before adding the filesystem), which might be called a "3.49 MB" floppy.

Hence, I propose that we use floppy disk format or floppy disk image to refer solely to formats or images having up to 3.5 MiB of total capacity, and that anything above that should be called a superfloppy. Of course, floppy formats or images must represent a single device, starting in a boot sector (or be fully zeroed). Of these, all that have a capacity >= "1.44 MB" would receive a Medium Type Byte = 0xF0.

Anything having a MBR and partitions (regardless of being a ZipDisk, a pendrive, or other hardware, or their respective images) would be called a "hard disk image/device" or "hard-disk-like image/device", and have Medium Type Byte = 0xF8.

Please let me know your opinion.

[rloew]

Well... since we've agreed that a filesystem is a bunch of bytes (or whatever) that can be divided in a System Area and a Data Area (we did agree to that, didn't we?), I'm thinking that there's one more concept I'd like to find a common terminology for:

(i) By looking at the floppy disk format list I posted, we can easily see that the maximum a common "1.44 MB" FDD can actually format is a 83 * 21 * 2 * 512 floppy, which means 1,784,832 bytes or 1.70 MiB (before adding the filesystem), the so called "1.74 MB" floppy.

(ii) The "2.88 MB" floppy uses a special FDD, which can create twice the sectors the normal one can.

So I conclude that the most extreme floopy format possible (although I've never heard about anyone ever having formatted a floppy like this) should be a 83 * 42 * 2 * 512 floppy, which means 3569664 bytes or 3.40 MiB (before adding the filesystem), which might be called a "3.49 MB" floppy.

Hence, I propose that we use floppy disk format or floppy disk image to refer solely to formats or images having up to 3.5 MiB of total capacity, and that anything above that should be called a superfloppy. Of course, floppy formats or images must represent a single device, starting in a boot sector (or be fully zeroed). Of these, all that have a capacity >= "1.44 MB" would receive a Medium Type Byte = 0xF0.

Anything having a MBR and partitions (regardless of being a ZipDisk, a pendrive, or other hardware, or their respective images) would be called a "hard disk image/device" or "hard-disk-like image/device", and have Medium Type Byte = 0xF8.

Please let me know your opinion.

Guess again. Amigas Format 1802240 Bytes on a HD (1.44MB) Floppy using their standard Format. Non-Standard formats can easily reach 1966080 Bytes or more.

USB Drives can be used with or without a MBR. They still use 0xF8.

I think that 0xF0 is needed for Floppy-like Drives (Drives that mount as A: or B:). Otherwise use 0xF8.

DOS 7 handles A: and B: Drives differently than C: or higher.

[dencorso]

OK. Except for formats having their own 0xFX code, 0xF0 for what will become A: or B: and 0xF8 for all other cases is a rule-of-thumb that makes sense to me.

However, 1966080 Bytes is 1.88 MiB, which is still < 3.5 MiB... and I don't think Amigas can use a "2.88 MB" drive.

Or are you suggesting we should put the floppy/superfloppy frontier at 4 MiB GiB? What is a superfloppy for you?

Please elaborate.

[jaclaz]

OK. Except for formats having their own 0xFX code, 0xF0 for what will become A: or B: and 0xF8 for all other cases is a rule-of-thumb that makes sense to me.

However, 1966080 Bytes is 1.88 MiB, which is still < 3.5 MiB... and I don't think Amigas can use a "2.88 MB" drive.

Or are you suggesting we should put the floppy/superfloppy frontier at 4 MiB GiB? What is a superfloppy for you?

Please elaborate.

There is the 2M formats too.

http://en.wikipedia.org/wiki/2M_(DOS)

the max capacity on ED disks is

~4,100,000 bytes (4004 KiB)

(4 Gib is seemingly a bit too much )

                                 +------------------------------------+
                                 ¦   Double  ¦   High    ¦ Extrahigh  ¦
 +-------------------------------+-----------+-----------+------------+------+
 ¦ Absolute record before 2M     ¦  820.0 Kb ¦ 1394.0 Kb ¦     --     ¦      ¦
 ¦ Maximum 2M capacity (2MF /M)  ¦  902.0 Kb ¦ 1558.0 Kb ¦     --     ¦ 5.25 ¦
 ¦ Minimum 2MGUI capacity        ¦  976.6 Kb ¦ 1639.8 Kb ¦ 1203.1 Kb  ¦ (5¼) ¦
 ¦ Physical limits (82 tracks)   ¦ 1001.0 Kb ¦ 1668.2 Kb ¦ 1228.8 Kb  ¦      ¦
 +-------------------------------+-----------+-----------+------------+------¦
 ¦ Absolute record before 2M     ¦  984.0 Kb ¦ 1722.0 Kb ¦ 2880.0 Kb  ¦      ¦
 ¦ Maximum 2M capacity (2MF /M)  ¦ 1066.0 Kb ¦ 1886.0 Kb ¦ 3772.0 Kb  ¦  3.5 ¦
 ¦ Minimum 2MGUI capacity        ¦ 1176.0 Kb ¦ 1972.0 Kb ¦ 3944.0 Kb  ¦ (3½) ¦
 ¦ Physical limits (82 tracks)   ¦ 1201.2 Kb ¦ 2002.0 Kb ¦ 4003.9 Kb  ¦      ¦
 +---------------------------------------------------------------------------+

jaclaz

[rloew]

OK. Except for formats having their own 0xFX code, 0xF0 for what will become A: or B: and 0xF8 for all other cases is a rule-of-thumb that makes sense to me.

However, 1966080 Bytes is 1.88 MiB, which is still < 3.5 MiB... and I don't think Amigas can use a "2.88 MB" drive.

Or are you suggesting we should put the floppy/superfloppy frontier at 4 MiB GiB? What is a superfloppy for you?

Please elaborate.

There never was a "2.88 MB" drive for the Amiga, but the principles used can be applied to the PC. I'm not sure that you can put three 8KiB Sectors in a single track but I think you probably can put one 16KiB Sector and one 8KiB Sector on a track. It is possible to put one 24KiB Sector on a track but you would need to do Error Detection in software.

Even putting 11 1KiB Sectors per track would achieve 3.52MB.

I never thought about the distinction between floppies and superfloppies. I always treated standard floppy formats as "floppies", anything else as "superfloppies", or I suppose possibly "subfloppies". I have never used a superfloppy. I called the up to 36MB El-Torito Images "extended floppies" as they use the standard floppy Geometry except for the number of Cylinders.

Only the A:/B: vs. C: distinction is really important.

[dencorso]

To me, common floppies formatted to 32 MB by LS-240 drives and those 40 MB click! from Iomega are superfloppies already. So the 36 MiB FAT-12 image we are discussing from the start of this thread *is* a supperfloppy image, not a floppy image. And it'll get A: on boot, and it has a single logical device starting in a boot sector, so it has all the characteristics of a floppy (or superfloppy). And that's why the original thread had superfloppies in the name, which ended up causing the split of the original thread into two threads. But then it dawned on me that it's not at all clear what idea each of the participants in this discussion has about what is a superfloppy. And I realized that not even to me it's actually clear how big a floppy may become, before starting to be a superfloppy. So I posted about reaching a consensus about it. It was relevant enough to cause a thread split, even if it may be irrelevant for practical purposes (I mean: actual usage or the way they are seen by any given OS).

[jaclaz]

If we have to draw a line somewhere, I would draw it, as hinted, right after the 2M 4003.9 Kb size, since that is "the biggest floppy you can have on actually largely mass produced hardware using standard floppy media" (a bit lousy as definition , but not worse than many others ).

While the LS-120 did have some diffusion, the LS-240 had so short a lifetime that the actual numbers are really low AFAIK (and only the LS-240 could make the 32 Mb floppy).

But I am with rloew, to me *anything* which first sector is a MBR and holds a partition table is a "HD-like device" and *anything* which first sector is a bootsector is a "floppy-like device".

jaclaz

[dencorso]

OK. But the table you provided is for 82 tracks. And almost all FDD made after 2000, including my quite unremarkable Samsung SFD-321B Rev. T4 (manufactured in Feb 2002), and the Mitsumi D359T7 I've just decommissioned, are capable of formatting/writing/reading 83 tracks reliably. This pushes up the max capacity on ED disks to ~4,150,000. Then I think 4.0 MiB as a round-number limit is a good number, after all. Can we agree on using it to define the frontier between floppy and superfloppy?

[rloew]

To me, common floppies formatted to 32 MB by LS-240 drives and those 40 MB click! from Iomega are superfloppies already. So the 36 MiB FAT-12 image we are discussing from the start of this thread *is* a supperfloppy image, not a floppy image. And it'll get A: on boot, and it has a single logical device starting in a boot sector, so it has all the characteristics of a floppy (or superfloppy). And that's why the original thread had superfloppies in the name, which ended up causing the split of the original thread into two threads. But then it dawned on me that it's not at all clear what idea each of the participants in this discussion has about what is a superfloppy. And I realized that not even to me it's actually clear how big a floppy may become, before starting to be a superfloppy. So I posted about reaching a consensus about it. It was relevant enough to cause a thread split, even if it may be irrelevant for practical purposes (I mean: actual usage or the way they are seen by any given OS).

I wanted the CD Floppy Emulation thread to be distinct from the SuperFloppy thread because it is about El-Torito Floppy Emulation on Optical Media. There are different considerations for these than there are for other Floppy-Like Devices such as the LS-120, LS-240, Clik etc. It was not about size. I pushed the El-Torito limit in Post #1. Now I have determined that there is no real limit.

But I am with rloew, to me *anything* which first sector is a MBR and holds a partition table is a "HD-like device" and *anything* which first sector is a bootsector is a "floppy-like device".

That is not what I said. I said Devices that Mount as A: or B: are Floppy-Like. Devices that Mount as C: or above are HD-Like.

USB Drives generally Mount as C: or above, so are HD-Like, but they can use a MBR or not use a MBR.

I will agree that a Drive that uses a MBR is HD-Like because it cannot be Mounted as A: or B:, but the Converse is not necessarily true.