[solved] Can't read 720K floppies

[abalone]

Re: Can't read 720K floppies

Well, this is embarrassing. I was using defective disks.

[Telengard]

Re: Can't read 720K floppies

How old are these 720K floppies?

[Snowhog]

Re: Can't read 720K floppies

[Ole Juul]

Re: Can't read 720K floppies

Well, this is embarrassing. I was using defective disks.

Usually 720s are older, thus better quality so you might just reformat them. It's the modern runs which sometimes have bad coatings. If they are defective because of writing defects or drive misalignments, then you can fix them using a bulk eraser. Also, don't forget that the 720 and 144 media have different magnetic coercivity. Good luck.

[sithlord48]

Re: Can't read 720K floppies

well its good to see at least you have a decent chance of using them, or at least new 720k floppys. that is if you can even buy new 720k disks.....

[Ole Juul]

Re: Can't read 720K floppies

They're getting hard to find but you can still buy new 8" floppies! Regular 3 1/2" DD are often available reasonably cheap on eBay etc. but new they cost about 3 times what they used to. Here is one source for a buck a piece. Luckily they will sell small quantities. http://www.floppydisk.com/buy.htm

[Telengard]

Re: Can't read 720K floppies

http://www.floppydisk.com/buy.htm

99 cents per disk for 5.25 DD? Outrageous! Just for reference, I used to buy 5.25 DD for 15 or 20 cents per disk in the 1980s.

[abalone]

Re: Can't read 720K floppies

I just take 1.44 MB disks and put a sticker over the left hole.

[Telengard]

Re: Can't read 720K floppies

I just take 1.44 MB disks and put a sticker over the left hole.

That is not a reliable way to make 720K floppies! The magnetic media of the two disks is not the same, and some floppy drives are more finicky than others. I learned this the hard way years ago.

[abalone]

Re: Can't read 720K floppies

Oh? Well, it doesn't have to be super-reliable, as long as I can carry some stuff from one room into the other that way... I'm not using them to *store* anything (got harddisks for that...)

[Ole Juul]

Re: Can't read 720K floppies

. . . Well, it doesn't have to be super-reliable, . . .

Well, it won't be.

I suggest formatting the 1.44s (18spt) to 720 (9spt) by using software instead. DD and HD have the same TPI (tracks per inch) but different sectors per track. Your formatting software should give you those choices. That way the drive knows what to do and that is what the hole is for - not to indicate sectors per track which is a software issue. If you cover the hole in the disk, the drive will think that it needs to use the higher amperage to the heads and the signal will probably bleed all over the place.

Knowing about the hardware can come in handy.
Here is a good floppy drive primer:
http://www.accurite.com/FloppyPrimer.html
Floppy disk formats:
http://en.wikipedia.org/wiki/Floppy_disk_format

[abalone]

Re: Can't read 720K floppies

IIRC the Amiga drive doesn't read the disks when the hole isn't covered. It doesn't work with HD disks unless it thinks they're DD disks. Or ...whatever the hole means to it, if anything.

I don't understand; of course they're formatted to 720K using software (how else?)

[Snowhog]

Re: Can't read 720K floppies

720K DD floppies.

Take a look at the fdutils application:

Description: Linux floppy utilities
This package contains utilities for formatting extra capacity
disks, automatic floppy disk mounting and unmounting, etc.
.
The package includes the following items:
.
- superformat: formats high capacity disks (up to 1992k
for high density disks or up to 3984k for extra density
disks);
- fdmount: automatically mounts/unmounts disks when they are
inserted/removed;
- xdfcopy: formats, reads and writes OS/2's XDF disks;
- MAKEFLOPPIES: creates the floppy devices in /dev;
- getfdprm: prints the current disk geometry (number of
sectors, track and heads etc.);
- setfdprm: sets the current disk geometry;
- fdrawcmd: sends raw commands to the floppy driver;
- floppycontrol: configures the floppy driver;
- general documentation about the floppy driver.
.
Note that these utilities do not work for USB floppy drives, because
these do not allow direct access to the floppy controller.

[Ole Juul]

Re: Can't read 720K floppies

. . . I don't understand; of course they're formatted to 720K using software (how else?)

Sorry abalone, I didn't mean to confuse. Yes, of course using software. However the little hole (controlling a switch) tells the drive what level of current to use on the heads when writing data. The current needs to match the media. I guess I was (probably wrongly) thinking that the Amiga had a 144 drive and you only had 720 disks.

Just to clarify, here is the basic explanation of why you can't always get away with plugging the hole:

A 144 disk will have media which is designed for a lower lever of magnetization than the media in a 720 disk. If you plug the hole in a 144, the drive will think it is a 720 and use the higher current - and thus the higher magnetisation which will overwrite the track and possibly even bleed through to the other side. A 144 uses a thinner layer of smaller particles in order to get higher bit density.

So if you give the drive a 144 disk which has the media which is meant for the lower current (meaning weaker magnetization) then the higher magnetization power of the 720 write current will overwrite the track. The higher current will spread the magnetization over a larger area. It will bleed further than the design called for. In other words the disk will read unreliably. It is that little hole in the disk that tells the drive which current level to use.

So, my suggestion to use software was intended to mean that you leave the hole alone so the drive knows what the correct current is for the media, and then make the actual format configuration with the software. That is use a command like "format f:720 /u" (or whatever it is) or pick from a menu or whatever. However, I was thinking that the Amiga had a 1.44 drive and you were using 720 media. That was probably a wrong assumption - I don't know what I was thinking. Sorry to confuse. Hopefully anyway, you now know why you can't use 144 disks in a 720 drive and expect them to be reliable.

[abalone]

Re: Can't read 720K floppies

Okay, thanks for clarifying. I think I had noticed before that my later disks (often repurposed MS-DOS driver disks and the like) were failing. Unfortunately, the "classic" Amigas didn't come with HD drives, and I'm not in the ...mood... to get one since an "IBM-compatible" drive wouldn't work.

This Amiga can read 720 KB "two-hole" (HD) disks without a sticker on, but formatting fails. Also, if the drive doesn't have the correct raygun settings for 1.44 MB media, this wouldn't help anyway, would it?

Maybe it's time to delete some old Amiga treasures from 880 KB disks (= 720 KB for MS-DOS) (or live with the odd failure (or get a really long network cable)).