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From https://www.filfre.net/2016/01/a-pirates-life-for-me-part-3-case-studies-in-copy-protection/

But balanced against the one great advantage of RapidLok for the legitimate user was at least one major disadvantage beyond even the obvious one of not being able to make a backup copy. In manipulating the Commodore 64 disk drive in ways its designers had never intended, RapidLok put a lot of stress on the hardware. Drives that were presumably just slightly out of adjustment, but that nevertheless did everything else with aplomb, proved unable to load RapidLok disks, or, almost worse, failed intermittently in the middle of game sessions (seemingly always just after you’d scored that big Silver Train robbery in the case of Pirates!, of course). And, still worse from the standpoint of MicroProse’s customer relations, a persistent if unproven belief arose that RapidLok was actually damaging disk drives, throwing them out of alignment through its radical operations. It certainly didn’t sound good in action, producing a chattering and general caterwauling and shaking the drive so badly one wondered if it was going to walk right off the desktop one day.

The belief, quite probably unfounded though it was, that MicroProse and other publishers were casually destroying their customers’ expensive hardware in the name of protecting their own interests only fueled the flames of mistrust between publisher and consumer that so much of the SPA’s rhetoric had done so much to ignite.

This is a good description of the pros and cons of RapidLok; the only thing I have issue with is the first line of the second paragraph, 'quite probably unfounded', a claim for which the author provides no justification.

I remember that floppy drives did sometimes go out of alignment. Code that produced an unpleasant hammering sound from the drive, was really doing what it sounded like: repeatedly hammering the read/write head against the stop. It seems physically likely that this will tend, over time, to knock the head out of alignment. In other words, a reasonable default would be that the belief that RapidLok damaged floppy drives, was well-founded.

Is there any evidence to the contrary?

Did such code really knock floppy drives out of alignment?

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    I wonder exactly what "knock the head out of alignment" even means. Does the head contain two components that need to be aligned in a particular way and are held in that position merely by friction? Jan 30, 2023 at 10:46
  • This question would be so good on a nerd version of Mythbusters. Jan 30, 2023 at 17:14

1 Answer 1

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Many home computer floppy drives (some 1541 variants, and also e.g. Apple II drives) had no track zero sensor. That means the only way to get them to a known position was indeed to hammer them repeatedly against the stop. And as this was intended operation, it didn't knock anything out of alignment.

I am not familiar with RapidLok, but if the reason they produced the hammering sound on slightly misaligned drives was that the drives couldn't properly read some data, and then the firmware went into readjustment mode, and that's all that happened, then that is no reason for concern.


Given that the materials of which the drives were made, were not infinitely rigid

Not infinitely, certainly...

But here is a real-life situation: The Apple II floppies "hammered" on every reset and reboot, and also like the 1541 when it couldn't read something, or had trouble copying something fishy (which I did quite often), and my floppies were fine over the whole lifetime and are still fine, and not out of alignment. So I very much doubt

and it had a probability distribution whose average was calculated to exceed the warranty period of the drive with a reasonable safety margin

that this was the case. After all, the warranty period is long over...


Reading up on head alignment on the 1541, it looks like the culprit for heads going out of alignment is high temperature:

Now, this “head banging” will usually cause no issues. But, if the unit is very hot, this may cause problems.

The pulley moved by the stepper motor is made up of alluminium. The motor shaft it is secured to is made up of steel. Different materials mean different thermal expansion. So, the pulley will have a greater thermal expansion than the shaft. The shaft is strongly forced on the hole of the pulley from the factory. But, as a result of thermal expansion due to the internal heat of the unit, the hole of the pulley will enlarge and the pulley will move with respect to the shaft. This unwanted rotation of the pulley related to the shaft will cause misalignment of the head.

This didn't happen with later Commodore drive models with external power supply (less heat). The Apple II drives also don't have an internal power supply, the electronics inside are much simpler, and there is more space and air inside - I've never experienced an Apple II drive running hot.

That means that yes, if RapidLok (or anything else) caused excessive "hammering" when the earlier drive model was already hot, the 1541 could go out of alignment. Still, "hammering" was intended usage; and when it happens shortly after the drive is switched on, the drive is still cold and then there is no risk.

And no, the drive was not designed just to stay aligned during the warranty time; it was the cross-effect with the drive getting hot. And likely this was never found out when testing the mechanics; the tests were likely done on an open drive, or only with the mechanics themselves.

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    'And as this was intended operation, it didn't knock anything out of alignment.' - be careful of that conclusion. Given that the materials of which the drives were made, were not infinitely rigid, I suspect a more physically realistic conclusion is that there was a finite number of times you could hammer the head before the drive would go out of alignment, and it had a probability distribution whose average was calculated to exceed the warranty period of the drive with a reasonable safety margin.
    – rwallace
    Jan 29, 2023 at 19:50
  • That doesn't say anything about whether the safety margin would be retained if you started using code that hammered the head much more frequently.
    – rwallace
    Jan 29, 2023 at 19:50
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    @rwallace Reliability testing is a bit of a black art, with the result that (good) manufacturers seriously overtest and derate the bits they can. It's a lot easier to ensure that the drive will "never" go out of alignment than it would be to determine that it'll last "long enough" even with manufacturing variances.
    – Sneftel
    Jan 30, 2023 at 11:16
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    @rwallace With the same argument, you could also argue "there was a finite number of times the drives could read a disk" - Both actions are "normal operation".
    – tofro
    Jan 30, 2023 at 16:56

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