Are there any 5.25'' floppy drives that are officially supported and which can read "flippy disks"?

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alt
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Re: Are there any 5.25'' floppy drives that are officially supported and which can read "flippy disks"?

Post by alt »

Hi everybody

I have been lurking around since I bought a KF board years ago, intending to use it for Amstrad CPC and Amiga disks preservation. Now I am posting for the first time because I have found something I believe hasn't been answered before.

Is there any chance that an unmodified PC 5 1/4 floppy drive could read flippy disks?

I am currently dumping C64 disks. I first modified two identical drives so one of them would pass the index signal to the other. It worked for disks without protection, i.e. d64 images, but DTC failed to create working .g64 images from the raw fluxes cooked with this trick.

I then started to look for drives that could be easily modified to read the disks at once. And I found this Toshiba ND-04DT-A (also marked as FDD6374R1W 02 on the label) that looked very good. It looked so good, that I saw nothing behind the head's module, nothing that may prevent the module to move backwards; so I decided to see what would happen if I forced it by adding -b-8 to the command line... and DTC reported no errors when dumping a flippy game!

Then I created a .g64 file from the fluxes, and it worked. I have dumped three disks so far with this drive, and they all seem to work properly. So, is it OK, or I am missing something?
brightcaster
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Re: Are there any 5.25'' floppy drives that are officially supported and which can read "flippy disks"?

Post by brightcaster »

You may have missed that this is a 40 track drive only! So no halftracks readable...

David
SomeGuy
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Re: Are there any 5.25'' floppy drives that are officially supported and which can read "flippy disks"?

Post by SomeGuy »

Are you sure this drive was not already modified?

Also, are you absolutly sure the all of the tracks are matching up? If the head just sits over track zero, it will still read SOMETHING but it will be the wrong track.

-B-8 would be wrong for a 40 track drive.

Also, many 360k drives have issues with GCR, but I have never tried a Toshiba.

On a standard PC drive, even if the head can physically move further back, the track zero sensor will stop it.

Could you post a stream dump made using this drive? Also, could you post some photos of this drive?
alt
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Re: Are there any 5.25'' floppy drives that are officially supported and which can read "flippy disks"?

Post by alt »

I have read somewhere that this drive is 40 track, but it actually reaches 83 tracks when calibrating.

Tomorrow I will take pictures of it and I will share the stream dump. Where should I upload it?
brightcaster
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Re: Are there any 5.25'' floppy drives that are officially supported and which can read "flippy disks"?

Post by brightcaster »

Yes, it looks as if the ND-04DT is 48 tpi and ND-04DT-A is 96 tpi. There are a lot of different boards also, so "Toshiba FDD6374" is the string to search for. (which appears to be very rare!)

David
alt
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Re: Are there any 5.25'' floppy drives that are officially supported and which can read "flippy disks"?

Post by alt »

This is the drive:

Image

Image

Image

Image

...and here is a sample of a stream dump (taken from "The Seven Cities of Gold" by Ozark Software/Electronic Arts).
SomeGuy
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Re: Are there any 5.25'' floppy drives that are officially supported and which can read "flippy disks"?

Post by SomeGuy »

OK, a couple of things: Pin 2 on that drive seems to be not connected. Additionally, the dump shows it is spinning at about 300RPM. With 80 tracks/96TPI, that makes it a quad density drive, not a 1.2mb drive.

That stream dump shows track mismatches on the first 4 tracks of the back side. That means the head is NOT stepping below track 0.

Oddly, there is also a track mismatch on the first side. That does not make sense.
brightcaster
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Re: Are there any 5.25'' floppy drives that are officially supported and which can read "flippy disks"?

Post by brightcaster »

Are you shure that the head steps really beyond track zero? It looks as if the head physically stops at track zero and reads track zero again and again instead of track -4, -3, -2, and -1. The first 4 tracks on the flippy side contain identical data and DTC reports a discrepancy between logical and physical tracks.

David

Edit: Uhpps, sorry SomeGuy was quicker ;-)
Last edited by brightcaster on Mon Oct 19, 2020 9:37 pm, edited 2 times in total.
brightcaster
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Re: Are there any 5.25'' floppy drives that are officially supported and which can read "flippy disks"?

Post by brightcaster »

On the positive side, you may just need to create the "Track Zero Bypass" to modify the drive!

David
alt
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Re: Are there any 5.25'' floppy drives that are officially supported and which can read "flippy disks"?

Post by alt »

Thank you for the replies!

I have modified the drive so it can move backwards a little bit more: it was quite easy on this model...

Image

Image

Now it moves backwards almost three milimeters further; but I am missing the point on the controller board modification. I may cut the track from pin 33 to GND -but where should it be connected to? Which signal should I look for? Many thanks!
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