Yellow isn't good enough?
#1
I've tried reading about five dozen Amiga floopies on my charter cruise with the SuperCard Pro. I'm using a generic drive I had in the pile. Most disks seemed to have read well. One or two yellow blocks here or there. I've improved the reading on some disks by cleaning the inside magnetic-media cookie with a cotton swab dipped in isopropyl. I'm keeping the head clean that way, too. All ordinary disks - no copy protection.

I've spotted a failure mode on some of these old disks: the cookie becomes unglued from the metal hub, so turning the hub doesn't turn the media. Any advice?

I had maybe two or three disks that didn't read well at all. The manual wasn't clear about what green/yellow/red really meant. I found a post here that said that yellow should mean the data was still good, but I'm finding that it is a bit more arbitrary than that. Some yellows bring good data, others don't. There's no log file. Where can I get a better idea of what's happening during a read?

I'm opening the ADFs in Windows 7 explorer with ADFview. I'm examining ADF files in hex. If nothing's read because of a failure of the disk (see above), the ADF starts out full of zeroes. When there's some data read, but it's failing to open as ADF, I'm seeing areas that appear to be filled with non-random garbage like "DOSx" where byte 'x' counts up from 0x00, or changes to "DOWx", etc.

Once I had a blue-screen BSOD crash pointing to the FTDI driver when I disconnected the USB cable from the computer. Ouch.
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#2
In cases where the plastic disk has broken free from the center hub can be repaired by using a drop of "super glue" on the tip of a needle and place the glue where the metal meets the plastic. However, the index alignment is no longer valid.

Yellow means that SOME sectors on the track are good. Unless you get GREEN, there will be errors. The sector data is decoded if the sector header is found. If there is no header, there is no possibility of data being recovered because there is no way of knowing where it is. It is possible that the checksum for the data block is invalid and there is data there, which is could be why you would see something in the sector data area that looks funny. There is no log file generated.

I have never seen a crash with any version of the FTDI drivers before, and I have been using FTDI chips for the last 10 years in my products. So, that must be a Windows USB problem you are having with your setup.
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#3
(02-27-2015, 11:37 AM)admin Wrote: In cases where the plastic disk has broken free from the center hub can be repaired by using a drop of "super glue" on the tip of a needle and place the glue where the metal meets the plastic. However, the index alignment is no longer valid.

Are you saying there's no chance to read the existing data at that point - that my only choice is to reformat, and then the disk could be used?

I tried some gel superglue and it didn't hold. I can try again.
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#4
You can try cleaning the disks besides cleaning the heads. If SuperCard Pro can't extract the data, then nothing will. The bitcell window for an Amiga's disk controller is about +/- 12%, but SuperCard Pro's bitcell window is +/- 49%.

If you decide to format a disk, try using the media integrity tester in the utilities menu. That will tell you if that media is good. Don't do this to any disk you want to keep, as it wipes it out!
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#5
(02-27-2015, 09:27 PM)admin Wrote: The bitcell window for an Amiga's disk controller is about +/- 12%, but SuperCard Pro's bitcell window is +/- 49%.

By "bit cell window", do you mean the ability to find the original index pulse on the tracks? Obviously, without any clue from the old glue (which I only be be able to see if I disassemble it all), I wouldn't know the original orientation in relation to the slot on the metal hub.
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#6
No, this has nothing to do with the index pulse.

The bitcell is the duration of a flux pulse. A drive turns a magnetic flux transition (N-S, or S-N) into a square wave that lasts a period of time based on how long the flux transition takes. Typically, these transitions will be 2us, 4us, 6us, 8us, etc. depending on the exact disk format. When a disk ages, the North/South magnetic fields change, so bits will "move" (lengthen or contract). The standard floppy controllers allow a range of 10%-12% of the expected bitcell width for valid data. It is very common that the data can 20% or more depending on how it was stored.
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