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Floppy disks only accessible part of the time?


adamantyr
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So I have been reading some old 5 1/4" disks and copying contents to my Lotharek drive... and I notice an odd pattern which has repeated for EVERY disk so far:

 

It reads correctly once, but then immediately fails with "no disk in drive" errors. It occasionally lets me copy several files in a row to the other drive, but fails on others and won't re-read the disk unless I open the drive, pull the disk out, and push it in again.

 

My question is, is this just the fact my 5 1/4" disks are just over 30 years old and the low level formatting is dying? Or is it because I hooked up the drive to an edge connector that followed a pin connector with a twist? It SEEMS to work with that, it's the inconsistency that's maddening.

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Cables with twists shift the drive select line one step for each twist. The idea is that if you have all shifted cables, you strap all drives to react as number zero.

On the other hand, if you have all straight cables, you have to strap the drive select in the drives as DS0, DS1, DS2 etc.

 

If you think carefully about what you do, you can mix the two. If you have, from the controller, a straight cable, a twisted one and another straight cable, to connect three drives, you have to strap the drives like this:

  1. The first drive is set as DS0. It will react as DSK1.
  2. The second drive is also set as DS0, but due to the twist everything is shifted one step, so it will react as DSK2.
  3. The third drive is set as DS1, but since there's one (but only one) twist on the way to this drive, it will react as DSK3.

If you by accident map more than one drive to the same number, then you'll get problems.

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Hmm, yeah, I think it's because there is a twist in the cable going to my 5 1/4" drive, it's screwing up the assignment. It may also be mixed with the Lotharek not configured right to emulate DSK2. I'll need to (sigh) pull the whole bloody thing out and screw with settings until it is working correctly 100% of the time for all three drives.

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The 5 1/4" drive is in good working condition. If it wasn't, it would just fail to read disks 100% of the time, or it would do so in an inconsistent weird fashion. The fact it's so regular makes it more likely to be a configuration problem.

 

It's not 100% needed either. I like having one for access purposes but I won't be making use of it often.

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No, nothing works properly except the Lotharek drive. It works fine on DSK1 alone, but DSK2 doesn't work. That may be because the jumper settings aren't right; I've asked numerous times what they should be set to on the TI for DSK1 and DSK2 access and no one is answering.

When I get home tonight I'll have to open it all up and pull it out. The one thing I didn't try was the closer edge connector with no twist on the 5 1/4" drive because the finger-pinching annoyance of trying to hook both drives up and get them into the box without anything getting disconnected is a major pain.

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If I remember correctly, in the PC floppy cable configuration there is a separate motor enable and drive select line for Drive A and Drive B (pins 10,12,14,16). The TI controller uses one motor enable line and 3 drive select lines on those same 4 pins. When used with a TI controller, the twist in the cable re-routes the single motor enable to one of the drive select lines. I no longer recall which drives are affected and how, but you would be better off eliminating the twisted cables from your setup if at all possible.

Edited by InsaneMultitasker
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Solved it... I forgot my 5 1/4" needed the dip switch changed to 3. :) the Lotharek also needed a switch turned to make dsk2 operative.

 

I also moved the pin connector down my cable and cut off the twisted excess. It's been a long while since I did disk cable surgery...

 

That also explains why my extra drive failed to work, I'll have to change it to dsk4, if I want to use it. I don't think I will though, I only want a floppy drive for compatibility and transfer of software.

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