Wipe only

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KFX99
Posts: 14
Joined: Sun Jul 23, 2017 7:52 am

Wipe only

Post by KFX99 »

Hi,

is there a way to perform a wipe only on a disk using DTC?

Regards

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IFW
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Joined: Mon Nov 08, 2010 2:42 pm

Re: Wipe only

Post by IFW »

Not directly, but you could create e.g. an IPF or G64ext image where each track is marked as unformatted, and writing those images back to a disk would result in a perfectly wiped/unformatted disk.
However, keep in mind the head footprint is different at various TPI sizes, so traces of track data might remain depending on how previously the disk was used.
Note, that writing already changes a track to noise first.

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mr.vince
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Re: Wipe only

Post by mr.vince »

Wiping a disk with a drive is not what you want when you want to unformat it. You will want to degauss it, e.g. with a very strong magnet.

KFX99
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Joined: Sun Jul 23, 2017 7:52 am

Wipe only

Post by KFX99 »

> you could create e.g. an IPF or G64ext image

How could I create that manually? It is quite difficult to get a disk that is really unformatted and read this one using DTC to get image data with unformatted tracks ...

> you will want to degauss it, e.g. with a very strong magnet.

The problem with magnets is that they produce a polarized field. I do not want to create disks that have their magnetic particles all aligned and that magnatize the R/W head which on the other hand will then attenuate the magnetic data of good disks or even kil them.

I do know that there is an erase head built into the R/W head. I would have to investigate some schematics to see if setting write gate to active will enable the erase circuit. At least the erase head does his job when a drive performs a format ...

In other words, to degauss a disk we need a high frequency magnetic field (my high-end tape recorder uses 100 KHz to erase a cassette) but the price of professional degaussers is insane.

CU

brightcaster
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Joined: Fri Nov 08, 2013 10:48 pm

Re: Wipe only

Post by brightcaster »

Every CRT-television or monitor contains a simple degausser made of a coil (working with mains at 50Hz) and a PTC-resistor. Similar devices are used by watchmakers to degaus mecanical clocks.

They cost less than 20 EUR new at eBay!

There is no need for that high frequency commonly used in tape recordes if you only want to degaus the media. The high frequency is only needed for lo distortion with premagnetizing while recording analog data!

But it is important to fade out the power supply or move the coil away from the media slowly, because of the hysteresis of any magnetic material. Otherwise you will keep the micromagnets orientated to a certain direction. While lowering the magnetic field slowly to a zero degree, you leave them in disorder (noise).

David

KFX99
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Joined: Sun Jul 23, 2017 7:52 am

Wipe only

Post by KFX99 »

brightcaster wrote:
Sun Aug 06, 2017 8:27 pm
Every CRT-television or monitor ....
I know about those and how to use them. I was just thinking if it can be done as well by maybe activating write gate for one revolution on all tracks while simply sending no data.

IFW already explained how this could be achieved. The problem is, that I do not have any empty disk. Okay, I could create one using a degaussing coil, but I do not want to buy one to create one single disk - I already have so much stuff...

SomeGuy
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Joined: Wed Feb 18, 2015 8:18 pm

Re: Wipe only

Post by SomeGuy »

You are just wanting to create a blank disk image? I haven't tried this, but what might work is to take an existing stream file image, find a track that is blank (On a 40 track disk, track#40, 41, 42 are usually blank) and copy that track file over all of the other tracks. Then when you write the stream to a disk all tracks should report as "unformatted". Note that the KF will always write one signature track (very annoying on a 40 track drive where all extra tracks are formatted - it will bang the head thinking it must be able to get up to track 80).

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IFW
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Re: Wipe only

Post by IFW »

Yes, DTC wipes the track asserting WG and not generating any flux reversals - that's the only way to do it with a drive. Due to index signal jitter you actually want to do this for more than a single revolution measured.

Is there any use-case for this? (keeping in mind that the disk may not really be erased due to head footprint...!)

ZrX
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Re: Wipe only

Post by ZrX »

KFX99 wrote:
Sat Aug 05, 2017 12:17 pm
The problem with magnets is that they produce a polarized field. I do not want to create disks that have their magnetic particles all aligned and that magnatize the R/W head which on the other hand will then attenuate the magnetic data of good disks or even kil them.
Not sure if this counts with diskdrives. Tape heads are most often contained in metal cases that can be magnetised. Diskdrive heads on the other hand are a big slab of ceramic with a very tiny ferrite element wound in fine copper wire.

KFX99
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Joined: Sun Jul 23, 2017 7:52 am

Wipe only

Post by KFX99 »

IFW wrote:
Fri Sep 08, 2017 5:34 pm
Is there any use-case for this? (keeping in mind that the disk may not really be erased due to head footprint...!)
Well, I was just asking because I stumbled over something saying "use of really empty / unformatted disks is strongly recommended". This was quite some time ago and may be even irrelevant due to the fact, that DTC cannot recover archived data (i.e. write back raw stream files containing non-index-aligned data), which I did not know by the time when I read about "do use an unformatted disk".

Being unable to recover a damaged original containing non-standard format or refresh the magnetic recording by backing it up and rewriting stuff I kind of gave up.

Fortunately there is some 3rd party software that does a great job in creating user readable information from the stream files like interleave, skew, sector statuses, recording method and so on.

I am not saying that it still would be great if it was possible to recreate an original on a really blank medium, but obviously I cannot do anything about it that there is no way for the time being.

Regards

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