Can KryoFlux detect drive capabilities ?

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wuffe
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Can KryoFlux detect drive capabilities ?

Post by wuffe »

First of all sorry if this question is plain and simple stupid - but I do not have access to my KryoFlux for the next couple of days and hence cannot test this myself.

Can KryoFlux detect drive capabilities such as [SS/DS], [SD/DD/HD/QD], [48 TPI,96 TPI,100 TPI] ?

I'm specifically asking in respect to 5.25" drives that comes in quite a lot of variations

Last if it can detect such capabilities where does it report about it (GUI) ?
TeaRex
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Re: Can KryoFlux detect drive capabilities ?

Post by TeaRex »

AFAIK there is simply no way a floppy drive could report such data to the FDC (kryoflux or any other). That's why you still have to select the drive type in the BIOS Setup even these days with PC floppy drives, when almost everything else is auto detected.

The only thing that kryoflux can detect is whether a drive is 40 tracks or 80 tracks - simply by seeking and seeing what happens, as in the "dtc -c2" command. I guess if you wanted to, you could pseudo-"detect" single sided drives by the fact that they either don't deliver any data for the back side or read the front side again (I don't know which); of course this "detection" could be fooled by a disk that has the same data on the front and back sides. And of course if you can read HD data from a disk, the drive is very probably a HD (or ED) drive, but you can't tell the other way since HD drives will of course produce DD data when there's a DD disk inserted.
wuffe
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Re: Can KryoFlux detect drive capabilities ?

Post by wuffe »

TeaRex wrote:AFAIK there is simply no way a floppy drive could report such data to the FDC (kryoflux or any other). That's why you still have to select the drive type in the BIOS Setup even these days with PC floppy drives, when almost everything else is auto detected.
That was also what I suspected...
TeaRex wrote: ... And of course if you can read HD data from a disk, the drive is very probably a HD (or ED) drive, but you can't tell the other way since HD drives will of course produce DD data when there's a DD disk inserted.
This may be a stupid question - but how would you specifically detect HD data ? the only way I can think of is by "counting" the amount of data in a track revolution or ???
TeaRex wrote: ... And of course if you can read HD data from a disk, the drive is very probably a HD (or ED) drive, but you can't tell the other way since HD drives will of course produce DD data when there's a DD disk inserted.
Unless I'm wrong this sets of another "fire" in respect to Kryoflux write support - writing DD to disks from a HD drive is known to blast neighbor bits. writing to HD disks from a DD drive is know loose data since only half of the needed the magnetic "power" is applied to the disk - but that is a whole other story - once write support is out for linux it is time to ask this question.
TeaRex
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Re: Can KryoFlux detect drive capabilities ?

Post by TeaRex »

wuffe wrote:This may be a stupid question - but how would you specifically detect HD data ? the only way I can think of is by "counting" the amount of data in a track revolution or ???
As far as I remember: if the time from one flux transition to the next is regularly well below 2 microseconds, it's a HD disk. If it's regularly well below 1 microsecond, it's an ED disk.
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IFW
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Re: Can KryoFlux detect drive capabilities ?

Post by IFW »

Just like TeaRex said. Drives modified to work with Amiga can report their drive type, through a serial protocol, but it is just a simple shifter logic giving a specific code number back, that only AmigaDOS could ever use and no ordinary drive can report anyway without an additional circuit.
MFM DD is 2us, MFM HD is 1us.
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mr.vince
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Re: Can KryoFlux detect drive capabilities ?

Post by mr.vince »

wuffe wrote:Unless I'm wrong this sets of another "fire" in respect to Kryoflux write support - writing DD to disks from a HD drive is known to blast neighbor bits.
Please enlighten me. Some source or link maybe?
wuffe
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Re: Can KryoFlux detect drive capabilities ?

Post by wuffe »

mr.vince wrote:
wuffe wrote:Unless I'm wrong this sets of another "fire" in respect to Kryoflux write support - writing DD to disks from a HD drive is known to blast neighbor bits.
Please enlighten me. Some source or link maybe?
I was a teenager in the 80'es and owned a C64 with a 1541 disk drive.
As a teenager I was always low on money and I clearly remember when family and other "grown ups" gave me packages of 5.25" HD disks as presents.
Typically it was packages of 5.25" HD disks that they've taken from their workplace etc - typically to be used with PCs.

Typically the HD disks would format - some wouldn't format without problems and needed several formats before they worked.
At first it would seem that the disks worked fine and would hold data/files - but they seemed to loose a bit or two here and there - quite fast (and quite annoying)

This observation of my own fits quite fine with the explanation that my 1541 drive would apply 300 oersteds coercivity where the (HD) disk was actually made for 600 oersteds coercivity - and hence the data written wouldn't always hang-on and sometimes faded out.
This problematic pattern was quite consistent - only with HD disks - (which I ended up hating)

My guess would be that others in this forum would have done the same expirernces back then...

Anyway here are some links:

http://www.retrotechnology.com/herbs_st ... .html#data
...
5.25 inch drives, 40 track (early drives 35 track):
...
iron oxide coating, 300 oersteds coercivity
...

5.25 inch drives, 720K DD, 80 track:
...
media: iron oxide coating, 300 oersteds coercivity
...


5.25 inch drives, 1.2M HD, 80 track:
...
HD media: cobalt coating, 600 oersteds coercivity
...

https://secure.wikimedia.org/wikipedia/ ... minifloppy
... Except for labelling, 5¼-inch high-density disks were externally identical to their double-density counterparts. This led to an odd situation wherein the drive itself was unable to determine the density of the disk inserted except by reading the disk media to determine the format. It was therefore possible to use a high-density drive to format a double-density disk to the higher capacity. This usually appeared to work (sometimes reporting a small number of bad sectors) — at least for a time. The problem was that the high-density format was made possible by the creation of a new high-coercivity oxide coating (after soft-sector formatting became standard, previous increases in density were largely enabled by improvements in head technology; up until that point, the media formulation had essentially remained the same since 1976). In order to format or write to this high-coercivity media, the high-density drive switched its heads into a mode using a stronger magnetic field. When these stronger fields were written onto a double-density disk (having lower coercivity media), the strongly magnetized oxide particles would begin to affect the magnetic charge of adjacent particles. The net effect is that the disk would begin to erase itself. On the other hand, the opposite procedure (attempting to format an HD disk as DD) would fail almost every time, as the high-coercivity media would not retain data written by the low-power DD field. High-density 3½-inch disks avoided this problem by the addition of a hole in the disk cartridge so that the drive could determine the appropriate density.

Also this site provides some quite interesting floppy stuff:

IBM 5.25 inch floppy drives and HD (1.2M) operation
http://www.retrotechnology.com/herbs_st ... html#12meg

720K 5.25" disks on 1.2Mb drives
http://www.retrotechnology.com/herbs_st ... .html#720K

360K 5.25" disks on 1.2Mb drives
http://www.retrotechnology.com/herbs_st ... .html#thin
...
Probably [because of] a combination of things... There are many tolerances to consider,and this particular scenario tends to magnify the effect of them. Some of the most likely are:

- Write current
- Type of head/exact width/mounting alighment
- Head load pressure
- Track to track alignment

Basically, after you have written the 48tpi disk with a 96tpi track, you will have two conflicting data patterns - These tolerances will greatly affect how these two patterns are perceived by the read head. The stronger the 96tpi track appears relative to the remainder of the 48tpi track, the more reliably the disk will read in a 48 tpi drive.
I've personally found that this "works" (writing 48tpi formatted disks at 96tpi and then being able to read them back at 48tpi) quite frequently, but I wouldn't trust anything valuable to it ... seen enough cases where it didn't work as well. - Dave Dunfield
/Uffe
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mr.vince
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Re: Can KryoFlux detect drive capabilities ?

Post by mr.vince »

Ok, but this only applies when using media that can't be identified - 5.25" disks. 3.5" disks come with a detection hole and I've said in other places that taping this hole is nonsense and people are very likely to lose data. If using the disk as intended - with the hole not taped, the drive will take care of the correct coercivity. In this case it's of course possible to write DD data to an HD disk. It just means the flux reversals are slower, which should not be a problem. You _might_ encounter a problem when using such a disk in a machine that can detect HD media, e.g. an HD disk with DD data in an Amiga 4000.

Apart from that, I don't see any problems. For 5.25" disks, which is currently not supported for writing, DTC will bring a command line switch to set the density signal on the drive. It will rely on the user picking the correct setting.


I was just wondering about
writing DD to disks from a HD drive is known to blast neighbor bits.
which is not true. The drive can write DD disks, it just needs to know and will adjust the coercivity. We are writing DD disks in HD drives all the time, and the drive sees the disk as DD, so all is fine. It is correct that there are drives out there that miss the DD detection which means they can read back fine (by just reading the flux changes) but can not set the correct coercivity while writing.
wuffe
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Re: Can KryoFlux detect drive capabilities ?

Post by wuffe »

Hi,

I think that you've misunderstood my post - I've from the beginning only addressed problems related to 5.25" drives and media - no 3.5" was ever mentioned by me - as I'm aware of the detection hole.
wuffe wrote: I'm specifically asking in respect to 5.25" drives that comes in quite a lot of variations
...
but that is a whole other story - once write support is out for linux it is time to ask this question.
mr.vince wrote: Apart from that, I don't see any problems. For 5.25" disks, which is currently not supported for writing, DTC will bring a command line switch to set the density signal on the drive. It will rely on the user picking the correct setting.
...
I was just wondering about
writing DD to disks from a HD drive is known to blast neighbor bits.
which is not true. The drive can write DD disks, it just needs to know and will adjust the coercivity.
Exactly my point - as all other comments in this post - this comment is in the context of 5.25" media and drives.
And please correct me if I'm wrong here - AFAIK 5.25" drives has no way of knowing and detecting this - and hence there is a potential risk of KryoFlux users accidentally destroys their 5.25" disks by writing with the wrong coercivity.
mr.vince wrote: We are writing DD disks in HD drives all the time, and the drive sees the disk as DD, so all is fine. It is correct that there are drives out there that miss the DD detection which means they can read back fine (by just reading the flux changes) but can not set the correct coercivity while writing.
I guess that this statement relates to 3.5" disks and drives ?
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mr.vince
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Re: Can KryoFlux detect drive capabilities ?

Post by mr.vince »

No, my statement would be correct for 5.25" drives as well. The density problem usually only arises while writing, reading should not be a problem.

But then... no real danger for disks. Just _set_ the correct density when writing a 5.25" disk and write again if you did wrong. You won't destroy anything permanently. II would recommend using a degausser anyway for pre-formatted 5.25" media, at least when writing 48TPI disks (e.g. C64) in a 96TPI (standard HD PC) drive. This will make sure there are no leftovers from a 48TPI head between tracks (as the 96TPI head will only write about half the width).
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