Any disadvantage to imaging Apple disks with a SuperCard Pro?

[natevw]

I recently acquired a SuperCard Pro and have been using it to image a variety of TRS-80 and Tandy 1000 disks so far, some Atari ones next, etc. But I also have some Apple disks and am aware of the Applesauce FDC that is made specifically for those.

As far as I can tell, the main difference is that the Applesauce is designed to work with original Apple drives, but modded to add an extra magnet and sensor to the spindle. Reading about the Disk ][ on Wikipedia, it sounds like Apple didn't include an index sensor on their drives and I imagine the retrofit sensor serves in place of this.

Were some Apple floppy disks themselves also missing the index hole? Otherwise I imagine my SCP in conjunction with a fuller-featured drive including the index sensor would be able to grab a flux-level image just as well as the Applesauce could, or am I missing something?

 

[SomeGuy]

Most 5.25" floppy disks had an index hole opening in their jacket because they were made for use in any 5.25" system.

However, most 5.25" disks did not have a SECOND index hole opening for use as a "flippy" disk. Without this, you may have problems just flipping the disk over to archive the second side.

If you encounter this, your options are
1: Punch a second index hole opening in the jacket,
2: Use a special "flippy modded" drive to archive both sides at the same time without flipping, or
3: Change drive jumpers, if provided, or find a drive model that will enter the ready state when no index is present. The SCP allegedly supports archiving with no index pulse, but I have had no luck with that. (The Kryoflux does not support that)

Another thing to watch out for are wiseguys who used Hard Sectored disks in Apple II computers. These disks have multiple index indicators through the disk cookie. They worked fine on genuine Apple II computers since they ignored the index, but not so much on IBM PC or other systems.

 

[Al Kossow]

A SCP doesn't use an Apple floppy drive, so you won't be able to image any of the exotic copy-protection formats that directly manipulated the head stepper

 

[natevw]

Ah, that makes some sense SomeGuy. However the drive I have has a read head on each side — so even without using the SCP "splice" mode wouldn't I be able to leave the disk "unflipped" — leveraging the index hole on the "correct" side — while still also capturing the back?

 

[SomeGuy]

Ah, that makes some sense SomeGuy. However the drive I have has a read head on each side — so even without using the SCP "splice" mode wouldn't I be able to leave the disk "unflipped" — leveraging the index hole on the "correct" side — while still also capturing the back?

Only if you have a "flippy modded" drive.

On a standard double sided disk, the tracks on each side are not physically opposite one another. There is an offset. It has to do with the way double sided head assemblies have to be made.

However, on a "flippy" disk, since there is only the one head, the tracks on each side wind up exactly opposite each other.

If you try to archive a flippy disk in a non flippy modded drive, the first side will read tracks 0-40 fine, but the second side will be missing the first few tracks. Because of the way a double sided drive's head is positioned, the only way to get those first few tracks is to step back BEFORE the normal track zero position. Of course, normal drives won't do that.

 

[natevw]

I think you just helped all the pieces click for me with this:

On a standard double sided disk, the tracks on each side are not physically opposite one another.

That was the part I had missed, and explains what in the world all those "flippy mods" are doing in the first place!

Now that I knew what to look for, I found https://www.lemon64.com/forum/viewtopic.php?p=574326&sid=842f8198ea6f292040b14965b1e391c9#574326 that re-iterates the same idea in a bit different words:

Yes, your drive is double-sided, but the positions of the two heads are slightly shifted in a way that the upper head (which would read the reverse side) starts at track 4 instead of track 1, so you would not have the chance to read the whole disk. Another problem is that the head is not exactly at track 4, so only a few disks may be readable.

Adding a spindle-based index sensor (and then just flipping the disks as the original users did) seems like the cleanest solution, certainly over messing with head or 0-track sensor alignments. I'll probably leave my SCP hardware setup closer to "stock" then, give its "splice" mode a fair shake when necessary, but keep in the back of my mind to look into modding a Greaseweazle or FluxEngine + magnetic sensor combo (e.g. https://github.com/davidgiven/fluxengine/issues/113) if I end up needing to deal with lots of flippy disks [but don't have budget for the Applesauce FDC which is admittedly a lovely looking bit of gear!].

 

[rittwage]

Another issue is the Apple disk drive can do quarter-steps, which no other drive controller will do. There may be a few titles that used this for protection (Spiradisk). I am sure it's rather rare, as there would be no way to mass manufacture these disks.

It may even be a myth...