Formatting HD floppies as DD

Jherek Carnelia · 02 February 2002, 19:56

What is the physical difference between HD and DD floppies (apart from the extra hole in the case!)?

I have a vague recollection that I once read that the only difference was the quality control on the media at manufacturing time. This leads me to wonder why I get so many disk errors when I try to use them as DD.

Could it be that there is some residual magnetism left behind by the HD formatting process that the DD format/stepping can't remove? And if this is indeed the reason could a de-gaussing of the disk return it to a state that would make it reliable?

Or I am I completely off the track and sector!!

I have hundreds of HD disks I could use but only 10 DD, so a solution to this problem would help a great deal!

Overdoc · 02 February 2002, 20:39

The problem is that HD disks need higher magnetical field strength when writing to them, so that they can keep the data. It doesn't matter if they are just being used as DD - the magnetism strength has to be higher with HD disks because the small megnetical particles on the disks surface cannot be directioned if the magnetism field strength is just as high as for a DD disk.

So the problem is that Commodore built various different drives into their Amigas, and it happens that some drives can bring up enough power to write to HD disks, while others don't

I can only say for sure that the Chinon FB-354 drive is able to write to HD disks, because I have used one of these for years in my A-500 and I have lots of HD disks which I have written to years ago, and they all still work like a dream

I have also heard that it might help with some drives if you cover the HD hole. I assume that some drives adjust the magnetism field strength according to the sensor for the HD hole, so that it will bring up more power if it detects a HD disk.

So, if you have a second drive for your Amiga you could try to format and write to HD disks with this drive ( also try the taping the hole trick ).
If the disks loose their data after a short period ( like 2 weeks or so ) then you are out of luck.
But if the disks keep their data then it should also be possible to read ( but not write ! ) them in drives that cannot write to HD disks.

Ok, now I stop before I write a book about this

Jherek Carnelia · 02 February 2002, 20:50

Thanks for that Overdoc, at least I know what the problem is now, and that a solution is possible.

02 February 2002, 19:56	#1
Jherek Carnelia Dazed and Confused Join Date: Dec 2001 Location: portsmouth/uk Posts: 242	Formatting HD floppies as DD What is the physical difference between HD and DD floppies (apart from the extra hole in the case!)? I have a vague recollection that I once read that the only difference was the quality control on the media at manufacturing time. This leads me to wonder why I get so many disk errors when I try to use them as DD. Could it be that there is some residual magnetism left behind by the HD formatting process that the DD format/stepping can't remove? And if this is indeed the reason could a de-gaussing of the disk return it to a state that would make it reliable? Or I am I completely off the track and sector!! I have hundreds of HD disks I could use but only 10 DD, so a solution to this problem would help a great deal!

02 February 2002, 20:50	#3
Jherek Carnelia Dazed and Confused Join Date: Dec 2001 Location: portsmouth/uk Posts: 242	Oh well... Thanks for that Overdoc, at least I know what the problem is now, and that a solution is possible.

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02 February 2002, 20:39	#2
Overdoc Commodore Collector Join Date: Aug 2001 Location: Austria Age: 53 Posts: 944	The problem is that HD disks need higher magnetical field strength when writing to them, so that they can keep the data. It doesn't matter if they are just being used as DD - the magnetism strength has to be higher with HD disks because the small megnetical particles on the disks surface cannot be directioned if the magnetism field strength is just as high as for a DD disk. So the problem is that Commodore built various different drives into their Amigas, and it happens that some drives can bring up enough power to write to HD disks, while others don't I can only say for sure that the Chinon FB-354 drive is able to write to HD disks, because I have used one of these for years in my A-500 and I have lots of HD disks which I have written to years ago, and they all still work like a dream I have also heard that it might help with some drives if you cover the HD hole. I assume that some drives adjust the magnetism field strength according to the sensor for the HD hole, so that it will bring up more power if it detects a HD disk. So, if you have a second drive for your Amiga you could try to format and write to HD disks with this drive ( also try the taping the hole trick ). If the disks loose their data after a short period ( like 2 weeks or so ) then you are out of luck. But if the disks keep their data then it should also be possible to read ( but not write ! ) them in drives that cannot write to HD disks. Ok, now I stop before I write a book about this

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