HD disks as DD? (was: how come?)

Drake1009 · 13 May 2002, 22:19

HD disks in my experience never work 100%. I don't think I've had one at all.

But then I don't think I've had a HD disk which worked 100% as HD disk on the pc yet.

Dastardly · 14 May 2002, 01:35

Werent Amiga games always free?

fiath · 14 May 2002, 23:52

I think they were referring to the reliabilty of HD disks used as DD disks...

i.e. it is not that good. Mind you, IMO HD disks are pretty unreliable as HD disks too!

Drake1009 · 14 May 2002, 23:55

Yeah I tried the HD with tape. Doesn't make them the least more reliable in my opinion.

Overdoc · 15 May 2002, 01:19

Whether a Amiga drive can format and save to HD disks as DD depends on the manfacturer of the drive.
The hole taping trick does work on old Matsushita drives afaik. ( these were built into very old A-500 kick 1.2 models )
Newer Amigas which have a Chinon FB-354 drive shouldn't have problems with HD disks. I have exactly thisdrive in my A-500 and HD disks which I copied stuff onto some yeras ago still work perfect !
Ok, I have also heard that this might depend on the disk manufacturer.
I have used lots of Escom HD disks, and also various other no-name disks all worked for me....
So I think it is more the drive than the disks !

Also it would be very helpful if everyone who has problems with HD disks could post his drive manufacturer and model number so that people can avoid these drives when looking for a replacement !

fiath · 15 May 2002, 20:47

Mine is the standard internal floppy that comes with the machine (A1200). Unfortuately - there does not appear to be any distinguishing marks on it to nail it down to a manufacturer...

Oh, I and I didn't have to do any tape trick (apart from in the PC) because my drive does not have a sensor there...

Overdoc · 15 May 2002, 21:20

Quote:

Originally posted by fiath
Mine is the standard internal floppy that comes with the machine (A1200).

Probably a Panasonic drive. Is there a number like JU257..... printed on it ?
And does it accept HD disks ?

The bad thing is that the problems with HD disks don't appear at once, but they appear with time. So it could well be possible that HD disks work at first after writing to them and then loose their data after one month or so.

fiath · 16 May 2002, 00:20

Ah, my mistake - it does have a label - on the rear near the connector - don't know why I didn't look there...

Anyway, it is a TEAC FD-235F - and your right, it accepts HD disks, but the data only lasts a very short time...

Amiga1992 · 16 May 2002, 05:34

My 1200 originally came with that TEAC drive too.. but it got busted so it was replaced with some otehr drive, forgot which one.

28 May 2002, 04:29

Hi overdoc & all kind eab forumers,

Overdoc, yr earlier post mentioned amiga drive model JU257 from panasonic. i thought this is a pc floppy drive. Did you mean it can be used for amiga too? Can anyone help me on this? I have a A1200 & I would like to have an extra floppy drive on hand just in case the original floppy which came with A1200 go bust.

Thanks!

28 May 2002, 18:18

how can a disk 'lose' the data on it? Surley something must wipe it off as disk cannot spontaneously lose data. can it?

fiath · 29 May 2002, 11:20

Actually yes it can, though it usually happens over a long period of time. It is called "bit rot" and is the bane of many a collector of floppy disk games.

An unformatted disk contains completely random data and even a random *amount* of data (perhaps this could be used for unbreakable encryption? :). This is called "magnetic noise". In fact, it is not just random - but indeterminate - successive reads yield different data - because the drive electonics cannot make head or tail of what the bits are. This fact is used in quite a few copy protection mechanisms.

There is no "disk structure" in place at all - this is put in place when formatting a disk for a particular system.

What happens is that the magnetic properties of the disk are initially pulled into order to represent bits (via an encoding like MFM to reduce error) when the disk is formatted and written to (rather simplified, there are complicated processes involved but you get the general idea).

Bits are represented by a "signal". The varience of this signal represents a 0 or a 1. Encodings (like MFM) are needed because floppy drives find it harder to read certain bit patterns than others.

The bits on the disk are held (actually represented by) the floppy magnetic properties. Now over a long period of time, due to the natural magnetism in the environment and general wear-and-tear, these magnetic properties "weaken" (and thus the drive has a hard time determining what they are - getting it wrong in the process) or the bits are actually corrupted (changed). The disk drive itself can also contribute to bit rot - just by reading the disk.

Using a disk that was not designed to hold the data you are putting on it (using HD disks to write DD data) obviously compounds the chances of the bit signals weakening.

Thus data can be "lost". This will eventually happen to ALL floppy disks.

This is the reason CAPS exists - to ensure any floppy disk data can survive in a form that is not effected by the bit rot that happens to the disks themselves.

BTW - Floppy disks generally last 5-10 years reliably if they are a good disk and not used much. Optical media (like CDROM) is not effected by any natural magnetical forces - and thus why they last a lot longer. But they are subject to general "wear and tear" and material decomposition - so again do not last forever - just longer than most people's life span. :o)

Overdoc · 29 May 2002, 13:33

The reason why data on HD disks, which were written to by a 'DD-only' drive, gets lost is that HD disks need a stronger magnetic field to bring the particles into a specific direction.
But DD drives cannot supply enough magnetical strength to do that, and so the particles on HD disks are not firm enough in their place and therefore can turn with time and flip over to the other bit.
This happens usually within some weeks or month, depeding on the magnetical surroundings they are used/stored.

Like Fiath said, this will happen to any disk after a long time, even if it was written with a drive suited for the disk ! But I think if disks are stored in a good place they will last quite longer than 10 years. ( I still have my first Amiga disks working which are ~10 years old, and also my first, over 15 years old C64 disks still work like on their first day

)
But I have heard that disks begin to rot away with time, and after this it will not even be possible to reformat them because the disk material ( the magnetical surface ) deteriorates

But I hope this will not happen to my C64 disks, because most of them have a protecting teflon surface !

@adf_son:

It depends on which JU257 exactly you have. Someone here on the board mentioned that some have jumpers on their back while others don't. The one with jumpers can be used for the Amiga easily, and even some models without jumpers can be converted by cutting a trace on the board and soldering one wire to another position.

Send me a mail or pm and let me know which drive you have exactly.

fiath · 29 May 2002, 14:06

Wasn't sure about HD disks - thanks for confirming that.

I didn't know about C64 teflon coating - cool!

Yeah, bad wording on my part.

I don't really mean 5-10 years life. I mean this is the quoted reliable life time from TDK. Disks could possibly last 30 years and beyond. The point is that they don't last forever and as we have seen, many disks have errors already - people just don't notice because they still load up / not effected until a later level / etc.

06 June 2002, 22:58

The trick to stick a Tape on the second hole of a HD-Disk is
useless. The Amiga has no system to recognize HD's (my 500 and 600 does not!)
What I found out:
On the PC format the HD with an undocumented MS-DOS command:
FORMAT A: /Y /SELECT
where /SELECT is the undocumented feature...
To test this command, type DIR A:
If MS-DOS tells you, that this disk is unreadable, then format it on the Amiga.

Overdoc · 07 June 2002, 00:31

Quote:

Originally posted by Bromosel
The trick to stick a Tape on the second hole of a HD-Disk is
useless. The Amiga has no system to recognize HD's (my 500 and 600 does not!)

Well, most Amiga drives don't have a sensor there, that's right. But some do have a sensor, in which case taping the HD hole does make sense.
The fact that the Amiga doesn't make use of it doesn't matter because it is the drive itself that does treat disks differently if it recognizes a DD or HD disk !
At least I know some people who have drives that do have the HD sensor and they confirmed that taping the hole did work for them

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13 May 2002, 22:19	#1
Drake1009 Registered User Join Date: Jul 2001 Location: Denmark Posts: 2,284	HD disks in my experience never work 100%. I don't think I've had one at all. But then I don't think I've had a HD disk which worked 100% as HD disk on the pc yet.

14 May 2002, 01:35	#2
Dastardly Into the Wonderful Join Date: Mar 2002 Location: England Age: 49 Posts: 2,335	Werent Amiga games always free?

14 May 2002, 23:52	#3
fiath Moderator Join Date: Jan 2002 Location: South East / UK Age: 46 Posts: 1,930	I think they were referring to the reliabilty of HD disks used as DD disks... i.e. it is not that good. Mind you, IMO HD disks are pretty unreliable as HD disks too!

14 May 2002, 23:55	#4
Drake1009 Registered User Join Date: Jul 2001 Location: Denmark Posts: 2,284	Yeah I tried the HD with tape. Doesn't make them the least more reliable in my opinion.

15 May 2002, 01:19	#5
Overdoc Commodore Collector Join Date: Aug 2001 Location: Austria Age: 53 Posts: 944	Whether a Amiga drive can format and save to HD disks as DD depends on the manfacturer of the drive. The hole taping trick does work on old Matsushita drives afaik. ( these were built into very old A-500 kick 1.2 models ) Newer Amigas which have a Chinon FB-354 drive shouldn't have problems with HD disks. I have exactly thisdrive in my A-500 and HD disks which I copied stuff onto some yeras ago still work perfect ! Ok, I have also heard that this might depend on the disk manufacturer. I have used lots of Escom HD disks, and also various other no-name disks all worked for me.... So I think it is more the drive than the disks ! Also it would be very helpful if everyone who has problems with HD disks could post his drive manufacturer and model number so that people can avoid these drives when looking for a replacement !

15 May 2002, 20:47	#6
fiath Moderator Join Date: Jan 2002 Location: South East / UK Age: 46 Posts: 1,930	Mine is the standard internal floppy that comes with the machine (A1200). Unfortuately - there does not appear to be any distinguishing marks on it to nail it down to a manufacturer... Oh, I and I didn't have to do any tape trick (apart from in the PC) because my drive does not have a sensor there...

16 May 2002, 00:20	#8
fiath Moderator Join Date: Jan 2002 Location: South East / UK Age: 46 Posts: 1,930	Ah, my mistake - it does have a label - on the rear near the connector - don't know why I didn't look there... Anyway, it is a TEAC FD-235F - and your right, it accepts HD disks, but the data only lasts a very short time...

16 May 2002, 05:34	#9
Amiga1992 Registered User Join Date: May 2001 Location: ? Posts: 19,646	My 1200 originally came with that TEAC drive too.. but it got busted so it was replaced with some otehr drive, forgot which one.

28 May 2002, 04:29	#10
adf_son Posts: n/a	Hi overdoc & all kind eab forumers, Overdoc, yr earlier post mentioned amiga drive model JU257 from panasonic. i thought this is a pc floppy drive. Did you mean it can be used for amiga too? Can anyone help me on this? I have a A1200 & I would like to have an extra floppy drive on hand just in case the original floppy which came with A1200 go bust. Thanks!

28 May 2002, 18:18	#11
Traquer Posts: n/a	how can a disk 'lose' the data on it? Surley something must wipe it off as disk cannot spontaneously lose data. can it?

29 May 2002, 11:20	#12
fiath Moderator Join Date: Jan 2002 Location: South East / UK Age: 46 Posts: 1,930	Actually yes it can, though it usually happens over a long period of time. It is called "bit rot" and is the bane of many a collector of floppy disk games. An unformatted disk contains completely random data and even a random amount of data (perhaps this could be used for unbreakable encryption? :). This is called "magnetic noise". In fact, it is not just random - but indeterminate - successive reads yield different data - because the drive electonics cannot make head or tail of what the bits are. This fact is used in quite a few copy protection mechanisms. There is no "disk structure" in place at all - this is put in place when formatting a disk for a particular system. What happens is that the magnetic properties of the disk are initially pulled into order to represent bits (via an encoding like MFM to reduce error) when the disk is formatted and written to (rather simplified, there are complicated processes involved but you get the general idea). Bits are represented by a "signal". The varience of this signal represents a 0 or a 1. Encodings (like MFM) are needed because floppy drives find it harder to read certain bit patterns than others. The bits on the disk are held (actually represented by) the floppy magnetic properties. Now over a long period of time, due to the natural magnetism in the environment and general wear-and-tear, these magnetic properties "weaken" (and thus the drive has a hard time determining what they are - getting it wrong in the process) or the bits are actually corrupted (changed). The disk drive itself can also contribute to bit rot - just by reading the disk. Using a disk that was not designed to hold the data you are putting on it (using HD disks to write DD data) obviously compounds the chances of the bit signals weakening. Thus data can be "lost". This will eventually happen to ALL floppy disks. This is the reason CAPS exists - to ensure any floppy disk data can survive in a form that is not effected by the bit rot that happens to the disks themselves. BTW - Floppy disks generally last 5-10 years reliably if they are a good disk and not used much. Optical media (like CDROM) is not effected by any natural magnetical forces - and thus why they last a lot longer. But they are subject to general "wear and tear" and material decomposition - so again do not last forever - just longer than most people's life span. :o)

29 May 2002, 13:33	#13
Overdoc Commodore Collector Join Date: Aug 2001 Location: Austria Age: 53 Posts: 944	The reason why data on HD disks, which were written to by a 'DD-only' drive, gets lost is that HD disks need a stronger magnetic field to bring the particles into a specific direction. But DD drives cannot supply enough magnetical strength to do that, and so the particles on HD disks are not firm enough in their place and therefore can turn with time and flip over to the other bit. This happens usually within some weeks or month, depeding on the magnetical surroundings they are used/stored. Like Fiath said, this will happen to any disk after a long time, even if it was written with a drive suited for the disk ! But I think if disks are stored in a good place they will last quite longer than 10 years. ( I still have my first Amiga disks working which are ~10 years old, and also my first, over 15 years old C64 disks still work like on their first day ) But I have heard that disks begin to rot away with time, and after this it will not even be possible to reformat them because the disk material ( the magnetical surface ) deteriorates But I hope this will not happen to my C64 disks, because most of them have a protecting teflon surface ! @adf_son: It depends on which JU257 exactly you have. Someone here on the board mentioned that some have jumpers on their back while others don't. The one with jumpers can be used for the Amiga easily, and even some models without jumpers can be converted by cutting a trace on the board and soldering one wire to another position. Send me a mail or pm and let me know which drive you have exactly.

29 May 2002, 14:06	#14
fiath Moderator Join Date: Jan 2002 Location: South East / UK Age: 46 Posts: 1,930	Wasn't sure about HD disks - thanks for confirming that. I didn't know about C64 teflon coating - cool! Yeah, bad wording on my part. I don't really mean 5-10 years life. I mean this is the quoted reliable life time from TDK. Disks could possibly last 30 years and beyond. The point is that they don't last forever and as we have seen, many disks have errors already - people just don't notice because they still load up / not effected until a later level / etc.

06 June 2002, 22:58	#15
Bromosel Posts: n/a	The trick to stick a Tape on the second hole of a HD-Disk is useless. The Amiga has no system to recognize HD's (my 500 and 600 does not!) What I found out: On the PC format the HD with an undocumented MS-DOS command: FORMAT A: /Y /SELECT where /SELECT is the undocumented feature... To test this command, type DIR A: If MS-DOS tells you, that this disk is unreadable, then format it on the Amiga.

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