ST floppy drive and HD disks

[Randy]

It has been noted numerous times that one should use DSDD floppys with the ST floppy drive because of magnetic coating, drive head, etc.  But the question I have is is it OK to use HD floppys when you have changed the ST floppy drive with a HD-type replacement drive?  You have the HD head in the floppy and presumably the HD software although the drive is configured to read as a DSDD disk.  It seems to me that HD floppys should be fine with an HD drive, or am I missing something here?  Thanks!

[ParanoidLittleMan]

It will work with HD floppy disks only if you cover hole for density detection on disks. And floppy change detection will most likely work not, unless you use some older Atari compatible floppy drive. Not to mention need to set drive as A, instead by newer drives default B .

 

[Randy]

Thanks PP!  I have already changed out the non-working Atari floppy for a compatible HD drive, think it was an Epson, it was on the compatibility list and it works fine reading and writing after the drive A change.  The question is though, using that replacement HD drive, can I use HD floppys without the worry that the data on the floppys will become unreadable over time.  I know about covering the HD hole and have successfully written to and read from HD floppys on the replacement drive, but will reading from the HD floppys become an issue later?  I would think no because I am using a HD floppy drive as a DSDD drive, but was not sure.  Thanks!

[ParanoidLittleMan]

No, HD floppies will not lose data, degrade faster than DD floppies. I have lot of them, with Atari files since 1991, and big % is still well readable. Comteam is best brand, btw. , according to condition of my HD floppies after many years.

Yes, Epson drives were Atari compatible, I had one in past, but did not see new ones over decades.

[Randy]

Thanks again, PP, your knowledge is excellent!

[atarian1]

My experience has been different. Using HD floppy disks as DSDD disks have been nothing but problems for me. I recommend using DSDD floppy disks since they can still be bought online.

[Randy]

On 5/25/2020 at 2:37 AM, atarian1 said:

My experience has been different. Using HD floppy disks as DSDD disks have been nothing but problems for me. I recommend using DSDD floppy disks since they can still be bought online.

question, are you using HD disks on a DSDD drive?  I can see that being a problem, but using HD disks on a HD drive that is running as a DSDD should be different, after all, the heads are different and presumably the signal to the heads would be different as well.  Is that true?

[atarian1]

The messages are confusing here. Your original post is correct. If your ST has the HD floppy circuit upgrade installed along with an HD floppy drive, then you can read/write HD and DSDD floppy disks. Unless you have an ancient HD floppy circuit, it should detect and switch between HD and DSDD floppy reading/writing automatically. The later ones I saw automatically switched the step rate between 3ms and 6ms for HD and DD access.

 

Don't cover the extra hole on HD floppies to make them DSDD. i remember a shareware author doing that and the floppy stopped reading after a few accesses.

 

 

[ParanoidLittleMan]

I would not go in so general bad opinion just because some HD floppy disks worked poorly as DD disks. All it depends from floppy (brand) self, and drive too. I had positive experiences. Surely is better to use genuine DD disks, if still can find some in good shape.

 

HD circuit in Atari ST(E):  I designed that one with automatic steprate control:  http://atari.8bitchip.info/autostep.html

Circuit needs signal for floppy density from drive, what is not present at Atari floppy connector, so it must be added. A

Ah, and that's ancient too by me - 11 years old ?

Now is really hard to find drive and disks in good shape. Everyone should make images of his important floppy disks - that's better than copying it. I did it 15-18 years ago.

[Randy]

11 hours ago, atarian1 said:

The messages are confusing here. Your original post is correct. If your ST has the HD floppy circuit upgrade installed along with an HD floppy drive, then you can read/write HD and DSDD floppy disks. Unless you have an ancient HD floppy circuit, it should detect and switch between HD and DSDD floppy reading/writing automatically. The later ones I saw automatically switched the step rate between 3ms and 6ms for HD and DD access.

 

Don't cover the extra hole on HD floppies to make them DSDD. i remember a shareware author doing that and the floppy stopped reading after a few accesses.

 

 

 

I still think there is a misunderstanding here, what I wanted to know is if you replace the DSDD drive with a HD drive, can you use HD floppys (with the hole covered) reliably.  No change to the drive circuit, just replace the bad DSDD drive with a HD drive that works.  Now, obviously the replacement HD drive will NOT write in HD format (1.44) but in DSDD format, unless there is a hardware change that a number of users, including exxos and PP have noted.  The replacement drive would be writing (and reading) in DSDD format onto the floppy, but the drive head, which has a finer gap, what would the physical signal written onto the floppy be?  Is it the same signal format as HD since it is a HD drive, which is to say, different magnetic spacing and flux density?  Or is the HD drive writing in the DSDD format, which is a different magnetic spacing and flux density to match the drive head?  I would surmise that the HD drive is going to write in HD format, that is what the head and electronics of the drive are made to do.  The signals coming into the floppy drive are bits/bytes, etc., they do not control the drive head current or spacing, the controller on the drive does that I would think.  The data from the computer tells the drive to write x bits at x location or side, the floppy controller then send the data to the head and stepper motor to magnetically record the data onto the spinning magnetic disk.  Since the head is shaped/designed for a floppy disk that is of a different magnetic properties and writes at a higher flux rate, the question remains, will an HD drive instructed to write at DSDD format write the signal in HD format onto an HD disk, i.e., higher flux density and spacing, and therefore be totally compatible with an HD floppy? Or, is the HD drive actually changing the way the head and stepper motor is writing the data onto the disks surface, i.e., with lower head flux current and wider spacing?

[ParanoidLittleMan]

As HD floppy drives were designed to work in DD mode too, no need to worry about those details - drive will set it properly when work in DD mode. Step works same, since tracks and their distance is same. What changes is only freq. of signal at head.

What can make HD disks less reliable in DD mode is different magnetic surface. But that depends from manufacturer, concrete revision.

Floppy drive gets already modulated signal from floppy controller chip, what is in computer. So, not getting bits, locations actually. But it must be syncronized, therefore is index signal, what indicates start of track, and then FDC chip starts to send modulated data, and it determines density too. If drive's rotation speed is not OK it will not work - when too fast not all data will fit in 1 rotation. If too slow signal freq will be useless. Floppy drive only controls head current and what goes with it.  Step works always same at drive - when gets step pulse just moves head one track in or out. Speed is determined by mechanic in fact. That's why old 5.25 inch drives have higher steprate, or better said longer time.  In case of Atari, when want to work in HD mode, need to set by SW steprate for FDC chip to virtual 6 mS, what in reality is 3 mS because of doubled chip clock rate. Or need to set clock to original 8 MHz instead 16 during step pulse.

[Randy]

Excellent answer PP, thanks!  BTW, do you know if the Mega Ste came with hd drives or DSDD drives?  I believe you have said before that the Mega STe can use HD drives, correct?

[zzip]

12 hours ago, ParanoidLittleMan said:

I would not go in so general bad opinion just because some HD floppy disks worked poorly as DD disks. All it depends from floppy (brand) self, and drive too. I had positive experiences. Surely is better to use genuine DD disks, if still can find some in good shape.

Maybe true, but after some bad experiences with HD disks in ST DD drives,  I wasn't about to risk more data by testing other brands, I went back to using DD disks ?

[Randy]

1 minute ago, zzip said:

Maybe true, but after some bad experiences with HD disks in ST DD drives,  I wasn't about to risk more data by testing other brands, I went back to using DD disks ?

And that makes complete sense, using DSDD floppys with DSDD drives is the best way I would say.  I have been watching the latest episode of Adrian's digital basement and this very same issue comes up and is discussed.

[snarkdluG]

41 minutes ago, Randy said:

Excellent answer PP, thanks!  BTW, do you know if the Mega Ste came with hd drives or DSDD drives?  I believe you have said before that the Mega STe can use HD drives, correct?

Older came with DD, newer with HD. Same with TT. However the Mega STe came pre pepared for HD if you only got DD. It's just a GAL chip and a HD drive I think. 

 

EDIT: WD1772 needs changing to AJAX. 

Edited May 27, 2020 by snarkdluG

[bluemonday]

I have a question about HD floppy disks on my ST.

 

My standard DS/DD floppy drive needs the heads cleaning. I have an cleaning kit with a HD disk. Is it OK to use this cleaning disk in my drive - will it still work? Should I cover over the HD detect hole? Thank you.

[ParanoidLittleMan]

I don't think that head cleaning disk needs some extra corrections - that's mechanical process, so all you need is to make it rotate - not with your hand ? but click on A: for that.

Btw. there is micro switch, #7 for activating HD mode in Mega STE, if there was DD drive by factory need to change it's pos. As was with mine, but there was already Ajax chip.

[bluemonday]

Thank you - will give this a go!

[Cubeast]

When you cover the detection notch of the HD floppy disk to fake the drive into assuming that it's a DD disk the drive uses the weaker DD mode to write to the disk. The disk has of course been designed for the much stronger HD mode. Verbatim's HD disk for example has 670 magnetic particles per inch with a coresivity of 720 oersteds whereas their DD disk has 310 magnetic particles per inch with a coresivity of 620 oersteds. You can I suppose think of that difference in terms of force like lightly scratching your name into clay vs heavily scratching into it and how one would last longer when exposed to the elements than the other....well there is a little more to it than that but you get the idea.   

[ParanoidLittleMan]

There is another difference beside magnetic signal strength: frequency, and it is 2x in HD mode, and that needs stronger signal. I don't think that example with scratching is good here. Then, duration of magnetic recording depends actually more from magnetic media quality, temperature, humidity etc. And of course need to avoid exposing it to magnetic fields.

 

Indeed it is best to use DD disks in DD drives, but if there is no such, HD might serve - not for longer storage, or at all for storage. There are much better, cheaper and faster ways for  that. Floppies only for running some SW on oldie. As data, file transfer media, if no better equipment at hand.

 

Btw. quality of floppy disks was pretty good in 80-es. Later it went down. As worse, what I had, and here talk only about DD disks  were some BASF ones - maybe not originals.

[Cubeast]

57 minutes ago, ParanoidLittleMan said:

There is another difference beside magnetic signal strength: frequency, and it is 2x in HD mode, and that needs stronger signal. I don't think that example with scratching is good here. Then, duration of magnetic recording depends actually more from magnetic media quality, temperature, humidity etc. And of course need to avoid exposing it to magnetic fields.

 

Indeed it is best to use DD disks in DD drives, but if there is no such, HD might serve - not for longer storage, or at all for storage. There are much better, cheaper and faster ways for  that. Floppies only for running some SW on oldie. As data, file transfer media, if no better equipment at hand.

 

Btw. quality of floppy disks was pretty good in 80-es. Later it went down. As worse, what I had, and here talk only about DD disks  were some BASF ones - maybe not originals.

Yes that's right, there are a whole lot of important distinctions between HD and DD and I am inclined to agree with you that my analogy is inadequate, I mean I am actually discarding certain things just for the sake of simplicity here. I mean there are just so many different factors that effect the longevity and readability of the magnetic recordings that would probably require their own separate analogies, such as the inverse square law for example.

 

I myself have quite a few adapted floppy disks and they seem to have held up alright but I also subscribe to the very same philosophy regarding their use as you have expressed.

[bluemonday]

Thanks for all your advice on this. I tried the cleaning using a HD disk but it hasn't fixed my problem of four bombs on boot if a floppy present but exploring a disk via clicking the A: icon works fine. But that is probably for another thread!