The drive is a Teac FD-54B-02-U. I am not opening the door at exactly track 20; this happens on every disk when the DriveType is set to 96tpi. What exactly does the TPI setting change about the imaging process? A guide I found on floppy disk controllers seems to confirm my suspicion the a step pulse moves one track:
> Step - This signal moves the head one track toward the disc's center or away from it. Movement occurs on the pulse's trailing edge.
Likewise this guide http://www.bitsavers.org/pdf/mitsubishi/..._Sep83.pdf implies a one pulse to one track setting:
> It is allowable to read (and sometimes write) a 48 TPI disk in a 96 TPI disk drive. But the software must command the controller to move two "96 TPI" trakcks for one 48 TPI track
So if I have "IBM 360K" selected as the disk type, and 96tpi selected as the drive type, and am imagining to a file, and "half-tracks" is checked but [probably although not reliably] greyed out — how far will the drive have advanced when the SCP app thinks it is on track 21?
My guess is that what's happening is that because a Single/Double 5.25" disk would have 40 tracks at 48tpi (source: https://en.wikipedia.org/w/index.php?tit...omposition) that SCP thinks it needs to double-step if I have the DriveType set to 96tpi. So by the time it gets to what it thinks is track 21 it has actually stepped 42 times and is at the end of the disk. I don't hear terrible grinding sounds after this but maybe since it's only bumping two at a time I don't recognize the noises enough.
There isn't a 5.25" 1.2MB disk type that I see (iirc from other forum hints one would use the 3.5" 1.44MB as an alias to that) but if there were I suppose it would have 80 tracks defined. So perhaps by setting my drive to 96tpi and then imaging as if it were a 1.44MB [i.e. 80 track, i.e. the "high density" version of either 5.25"/3.25" branding…] then I would get a high resolution version of my original mistake. Specifically, I would still get the noisy inner ring (of 40 tracks this time) but the outer ring would have the full 40 tracks of data too. There's no point in actually doing this — instead I will be more careful with my stepper motor now that I know — but just trying to puzzle out how everything interacts.
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In short, am I right to conclude the following?
1. Setting the drive type to 96tpi will cause a 48tpi drive to hit the end of its mechanism halfway through all the 48tpi disk formats (because the app will double-step between each track)
2. This is almost certainly a 48tpi drive, despite what some random forum post (http://www.vcfed.org/forum/showthread.ph...post170720) claimed about the Teac FD-54B model
> Step - This signal moves the head one track toward the disc's center or away from it. Movement occurs on the pulse's trailing edge.
Likewise this guide http://www.bitsavers.org/pdf/mitsubishi/..._Sep83.pdf implies a one pulse to one track setting:
> It is allowable to read (and sometimes write) a 48 TPI disk in a 96 TPI disk drive. But the software must command the controller to move two "96 TPI" trakcks for one 48 TPI track
So if I have "IBM 360K" selected as the disk type, and 96tpi selected as the drive type, and am imagining to a file, and "half-tracks" is checked but [probably although not reliably] greyed out — how far will the drive have advanced when the SCP app thinks it is on track 21?
My guess is that what's happening is that because a Single/Double 5.25" disk would have 40 tracks at 48tpi (source: https://en.wikipedia.org/w/index.php?tit...omposition) that SCP thinks it needs to double-step if I have the DriveType set to 96tpi. So by the time it gets to what it thinks is track 21 it has actually stepped 42 times and is at the end of the disk. I don't hear terrible grinding sounds after this but maybe since it's only bumping two at a time I don't recognize the noises enough.
There isn't a 5.25" 1.2MB disk type that I see (iirc from other forum hints one would use the 3.5" 1.44MB as an alias to that) but if there were I suppose it would have 80 tracks defined. So perhaps by setting my drive to 96tpi and then imaging as if it were a 1.44MB [i.e. 80 track, i.e. the "high density" version of either 5.25"/3.25" branding…] then I would get a high resolution version of my original mistake. Specifically, I would still get the noisy inner ring (of 40 tracks this time) but the outer ring would have the full 40 tracks of data too. There's no point in actually doing this — instead I will be more careful with my stepper motor now that I know — but just trying to puzzle out how everything interacts.
---
In short, am I right to conclude the following?
1. Setting the drive type to 96tpi will cause a 48tpi drive to hit the end of its mechanism halfway through all the 48tpi disk formats (because the app will double-step between each track)
2. This is almost certainly a 48tpi drive, despite what some random forum post (http://www.vcfed.org/forum/showthread.ph...post170720) claimed about the Teac FD-54B model