What is that horrible grinding noise coming from my floppy disk drive?


Wait, what's a floppy disk drive?

For those youngsters out there, floppy disks are where we stored data before the invention of the USB earring. A single floppy disk could hold up to two seconds of CD-quality audio. This may not sound like a lot, but it was in fact pretty darned awesome, because CDs hadn't been invented yet either.

Anyway, if you had a dodgy floppy disk (say, because you decided to fold it in half), you often heard a clattering sound from the floppy disk drive as it tried to salvage what data it could from the disk. What is that sound?

That sound is recalibration.

The floppy disk driver software kept getting errors back from the drive saying "I can't find any good data." The driver figures, "Hm, maybe the problem is that the drive head is not positioned where I think it is." You see, floppy drives do not report the actual head position; you have to infer it by taking the number of "move towards the center" commands you have issued and subtracting the number of "move towards the edge" commands. The actual location of the drive head could differ from your calculations due to an error in the driver, or it could just be that small physical errors have accumulated over time, resulting in a significant difference between the theoretical and actual positions. (In the same way that if you tell somebody to step forward ten steps, then backward ten steps, they probably won't end up exactly where they started.)

To get the logical and physical positions back in sync, the driver does what it can to get the drive head to a known location. It tells the hardware, "Move the drive head one step toward the edge of the disk. Okay, take another step. One more time. Actually, 80 more times." Eventually, the drive head reaches the physical maximum position, and each time the driver tells the hardware to move the head one more step outward, it just bumps against the physical boundary of the drive hardware and makes a click sound. If you issue at least as many "one more step outward" commands as there are steps from the innermost point of the disk to the edge, then the theory is that at the end of the operation, the head is in fact at track zero. At that point, you can set your internal "where is the drive head?" variable to zero and restart the original operation, this time with greater confidence that the drive head is where you think it is.

The amount of clattering depends on where the drive head was when the operation began. If the drive head were around track 40, then the first 40 requests to move one step closer to the center would do exactly that, and then next 43 requests would make a clicking noise. On the other hand, if the drive head were closer to track zero already, then nearly all of the requests result in the drive head bumping against the physical boundary of the drive hardware, and you get a longer, noisier clicking or grinding sound.

You can hear the recalibration at the start of this performance.

Bonus floppy drive music.

Bonus reading: Tim Paterson, author of DOS, discusses all those floppy disk formats.

Comments (41)
  1. Mott555 says:

    Has anybody else noticed the total lack of quality in modern 3.5" floppy disks? I needed a disk to do a BIOS update on a system last year and of course I didn't own any. I went to Office Max, all they had was a big box of 40. And out of those 40 disks, exactly 5 of them actually worked.

  2. Anonymous says:

    It's beem a long time since I messed up with floppies, but I think your explanation does not applies precisely to PC drives. If I remember well, PC floppy drives had a sensor for the track 0 position, so it would not need to bang at the end. The sound you hear on a PC is just the head moving up and down. On the other hand, Woz did not use the sensor in his Disk II interface for the Apple II (to reduce the hardware in the interface, latter Apple lowered the cost of the drives by demanding drives without the sensor).

  3. Anonymous says:

    I remember using a hole punch to make double sided disks.

  4. Anonymous says:
    1. I doubt many have noticed, given that most PCs nowadays don't have a 3.5" floppy drive. Most can boot from USB disk-on-key, and also update BIOSs from within Windows.
    2. Towards the end of their use, indeed I noticed quality was degrading. I always considered them an unreliable medium, and when backing up unto them, always made 2 copies.

    I generally like old tech… but not floppies. I've always considered them lousy, unreliable tech.

  5. Joshua Ganes says:

    I remember the days of archiving large files across multiple disks. You'd always have an error on disk 5 of 6, resulting in an unrecoverable error.

  6. MItaly says:

    @Jonathan: actually the data on 5.25" floppies of our old Commodore 64 survived fine for about 15 years, while almost everything stored on cassettes was corrupted here and there. But I think this was a lucky exception, floppies were way more unreliable than almost any media that we use today.

    Related: I still have around an ancient 3.5" drive from a PC of the early nineties. It was the best floppy drive I ever had, incredibly quiet and managed to read floppies that were unreadable for almost any other drive. I used it as a replacement for the crappy "stock" floppy drives on my PCs, until in recent years I got a motherboard with no floppy connector.

  7. Anonymous says:

    Was this post prompted by Jason Scott's recent plea to archive the data on our floppy disks? ascii.textfiles.com/…/3191

  8. SvenG says:

    I remember in the early 90s I had a 3.5" floppy drive that failed to read anything correctly (except occasionally by random chance). Disks were also noticeably loose in the drive, so obviously something was wrong. I removed the drive from the system and took it back to the store that I purchased it and proceeded to demonstrate the ill-fitting floppy… and it fit perfectly. They hooked it up, tested it, and it worked great

    I took it back home, reinstalled it in my PC, and the problem returned. The disks didn't fit right and didn't read right. So, what was the cause of this mystery? It turned out the drive worked fine as long as it didn't have any screws in it. An alignment issue or something meant that if I screwed it into the PC case, it was bent out of shape causing the problem. I replaced it and all was fine, but that was a weird issue.

  9. Anonymous says:

    As a bonus intellectual exercise, use the information provide to answer the question "why does this floppy disk work fine in my drive, but not any others?"

  10. Anonymous says:

    If only MS would update XP setup to support USB flash media when installing F6 drive controller drivers…the floppy was the worst invention of technology ever IMO.

  11. Anonymous says:

    A teenager recently asked me why drive lettering always seems to start at C: and never any other letter. Explaining that A: and B: were reserved for the first two floppy drives in the system didn't seem to help much, unfortunately.

  12. kinokijuf says:

    @Troll: there will be no further service packs for XP. Also, that part of the setup runs when there aren't any drivers loaded yet.

  13. Anonymous says:

    @kinokijuf:  Technically, there are drivers at that point in setup to drive the monitor and read the CD drive and the hard disk (and the floppy drive, if any), and some other things, but not enough to read a flash drive.  In Windows 7, on the other hand, I think that you can read things from a USB flash drive at that point in setup.  Of course, Windows 7 setup has SATA drivers running at that point in setup anyway, so the need for F6 drivers is less.

    But you're right, XP setup is not going to be improved at this point.  

  14. Anonymous says:

    @kinokijuf: There aren't any drivers loaded. That stage uses BIOS commands to read the CD and floppy.

  15. Mike Dunn says:

    Bonus exercise: Watch "War Games" with someone who's college age or younger, and watch their reactions to the technology in the movie.

  16. Anonymous says:

    @Daniel – Are you sure the sensor was for track 0 and not sector 0? I remember Apple II didn't use the hole in the disk to detect the position of the first sector, so you had to read the whole track until you find the signature for the beginning.

  17. Good grief, I just always assumed my floppy drive was flatulent.

  18. Anonymous says:

    Ah, nostalgia! The joy of having 30+ disks for Office 4.2 Professional, all lined up in order, and then having the installer ask for them in a random order! What fun.

    LS120s were slightly better – you could almost fit 1/5th of a CD on one 3.5" disk. The noise was pretty much the same, though.

  19. Anonymous says:

    More bonus floppy drive music: Phantom of the Floppera http://www.youtube.com/watch

  20. Anonymous says:

    I think kinokijuf was right and I was wrong (and Joshua yelled at kinokijuf).  

  21. Anonymous says:

    @Ivo – actually Woz ignored both sensors, you can read about it at wikipedia: en.wikipedia.org/…/Apple_II_series. I've also checked that PC floppy cables have pins for Index (sector 0) and Track 0 sensors: http://www.interfacebus.com/PC_Floppy_Drive_PinOut.html.

  22. Anonymous says:

    Technically, USB legacy emulation in BIOS could allow XP and Win2003 use an USB floppy drive or an USB stick, but those weren't presented by the BIOS as exactly the floppy drives. This is why one had to have a real legacy floppy on a real controller. Luckily, Win2003 is out of fashion already.

  23. jmthomas says:

    This noise is often the stepper motor itself, not just the banging against the stop.

    Each movement of the stepper motor can produce a small sound, and if the movement is done at the correct rate, acoustic principles amplify then into a raspy sound.

    If you start on one edge of the floppy and slew back and forth to near the other edge, you can produce a similar sound.  Position the directory at the start of the floppy, then rapidly writing small files near the other edge, to cause constant slewing back to the directory as each new file is opened/closed.  This is alleviated by caching the directory, which brings it own set of problems.

  24. Anonymous says:

    From a couple of years ago, here's Radiohead's Nude played on an assortment of computer parts:

    http://www.vimeo.com/1109226

  25. Anonymous says:

    What I never understood is why opening an Explorer window at Computer always causes the floppy to make the grinding noise.

    As for capacity, sure, only two seconds of uncompressed CD quality, but also 10 copies of a typical novel.

  26. Anonymous says:

    I was always fond of referring to floppy disks as WOM (write-only media).  Never sure you would be able to get anything off it.

  27. Mike Dunn says:

    When I read the title, I half expected the entire blog post to be "That's how floppy drives sound. I know it's weird if you didn't grow up with them."

    The C= 1541 was famous for its head-banging noise (which gets me a bit nostalgic, *tear*) and the fact that the collision was so hard, the drive could eventually get out of alignment.  Once that happened, you had the problem of being able to read newly-formatted disks, but not older disks, because the head was no longer exactly over the tracks.  And if you fixed the alignment, you had the opposite problem: you couldn't read those newer disks anymore.

  28. Anonymous says:

    What are these 3.5" and 5.25" floppies of which you all speak?

    I have a box full of floppies that are larger than that!

  29. rsola says:

    C:docs>copy a:*.*

    Data error reading drive A: Abort, Retry, Fail? r (Floppy drive makes noises…)

    Data error reading drive A: Abort, Retry, Fail? r (Floppy drive makes noises…)

    Data error reading drive A: Abort, Retry, Fail? r (Floppy drive makes noises…)

    Data error reading drive A: Abort, Retry, Fail? r (And so on…)

    I miss that. (Just kidding.)

  30. Anonymous says:

    Floppy drives aren't much more reliable than the disks in them… mine probably all need their heads cleaning.

    I only saw one LS120 drive and I wasn't using it with a LS120 disk but it seemed to be much better at reading floppy disks than a "real" drive.

    And bootable USB sticks aren't much use when third-party product X only installs on floppy drives.

  31. Anonymous says:

    Not only is there a Track 0 sensor, but Amstrad PCWs use it to tell if they've got 3.5" or 3.0" drives. They seek to track 0, turn off the drive motor, and see if the Track 0 signal goes away or not. On (IIRC) the 3.0" drives, the signal stops when the motor is off, while on the 3.5" drives it doesn't.

  32. Anonymous says:

    Who is this General Failure, and why is he reading floppy drive A?

  33. Anonymous says:

    It's not two seconds, it's about 8 seconds of CD quality sound.

    [You must be using one of those fancy modern floppy disks. The ones invented after CDs were invented. If you read past the second sentence you would've realized that I was talking about pre-CD-invention floppies. -Raymond]
  34. Yuhong Bao says:

    "Technically, USB legacy emulation in BIOS could allow XP and Win2003 use an USB floppy drive or an USB stick, but those weren't presented by the BIOS as exactly the floppy drives"

    Actually, the problem is that while XP/2003 Setup can detect and load drivers for USB floppy drives for after the kernel starts, the list of device IDs of USB floppy drives built into setup was incomplete, which means in most cases it wasn't being loaded:

    http://www.msfn.org/…/82711-using-a-f6-driver-with-usb-floppy

  35. Anonymous says:

    @Alex Grigoriev: BIOS interface to floppy, HDD and "legacy USB" are almost exactly the same. The only difference is that HDD are numbered from 128 to 255 while FDD are numbered from 0 to 127.

    Actually, if I had a time machine, I would make Windows XP installation look for drivers on any HDD the BIOS recognizes, and maybe, CD-ROMS, since Windows is able to load default drivers from the setup CD-ROM.

    Anyway, with a slightly improved SYSLINUX MEMDISK, it's possible to fake a FDD to Windows XP text mode setup.

  36. Anonymous says:

    A workaround for the XP setup / F6 storage drivers loaded from floppy disk is to make a custom cd with the necessary drivers built in using nLite.

  37. Anonymous says:

    Didn't read all of the comments, so if anybody did write this already, ignore it or try to bang my head onto the table ;)

    Actually, there's no error that can "accumulate". The floppy drives I know have a stepper motor with a step of one track, so there's nothing to accumulate except whole tracks (in which case, ONE recalibration should be enough to know exactly the current track number). Most likely it's just the effect that the r/w head might find a little bit different position when recalibrating due to mechanical tolerances.

  38. Anonymous says:

    @Raymond: [You must be using one of those fancy modern floppy disks. The ones invented after CDs were invented. If you read past the second sentence you would've realized that I was talking about pre-CD-invention floppies. -Raymond]

    That wasn't very clear, when you starts talking about 80 tracks floppies.

    [The number 80 was chosen randomly. Sorry for the misleading coincidence. -Raymond]
  39. Anonymous says:

    Makes me wonder why don't HDDs, being essentially the same device, ever need to recalibrate with the grinding noise.

    [Hard drives make recalibration noises too, but they usually sound more like clicks. -Raymond]
  40. kinokijuf says:

    @A. Skrobov: The HDDs have servo data prewritten in the factory.

  41. Yuhong Bao says:

    "because CDs hadn't been invented yet either."

    And more importantly, they were not recordable until the late 1990s.

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