Kids these days…

By sheer accident I stumbled on this document. In summary, it’s about a bunch of school kids working on a computer history preservation project and trying to archive a big box of floppies from George Alistair Sanger, a video game composer better known as The Fat Man. And they’re having all kinds of trouble. Inevitably this T-shirt came to mind (and yes, I do have one of those):

Kids Today...

It is is both amusing and amazing to me that someone might have trouble getting data off of a double-density 3½” floppy (Mac-formatted or not), or that anyone would even try getting software like Norton Backup or Central Point Backup running in DOSBox and expecting it to do anything useful.

I am not aware of any emulation/virtualization software which would support direct FDC access that such backup software often requires. It’s simply far too much of a niche market—the vast majority of floppies can be accessed as a straightforward block device, using OS-provided drivers. Supporting FDC register level access would require a completely different approach, taking over the FDC hardware and passing it through to a (single) VM.

It’s not that such technology is impossible. OS/2 2.x supported direct FDC access… but that was at a time when floppy drives were a requirement, not a rarity. Nowadays it’s simply much cheaper and simpler to buy an old PC and install DOS on it for such tasks.

However, the kids’ experience is probably not uncommon, and it does point to two common problems when preserving old data: Reading more or less exotic floppy formats, and extracting files from proprietary archival formats.

Kryoflux or a similar device can probably solve the first problem. It certainly shouldn’t be necessary to have an actual Apple II (or whatever) to read floppies that were used with an Apple II. The other problem may be much easier or much harder to solve. Virtualization and emulation can help with running old software (as long as the software is available!), but if old software needs direct hardware access, emulating it may be impractical. Not impossible, just more work than it’s worth.

Which is why keeping around an old PC with one or two floppy drives and running DOS is a good idea for anyone who needs to deal with old disks…

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22 Responses to Kids these days…

  1. dosfan says:

    YIKES !! I hope someone took the disks from these kids and sent them to the Computer History Museum for proper archival by someone who actually knows what they’re doing.

    DOS emulators and DOS backup programs ? If these are Mac disks then why not use a Mac to read them ? Even so Norton Utilities (which they apparently never heard of) would probably read them in maintenance mode running on an actual version of DOS.

    Finally there is no such thing as “PC DOS 7.01” – PC DOS 2000 is PC DOS 7.0 revision 1 and there is no reason any software would specifically require that version as there were no changes to the DOS API for any standalone retail version of DOS beyond DOS 5.

  2. raijinzrael says:

    Probably they fscked already the content from those old valuable pieces of history, specially if they didn´t took the proper security measures to disable write access to the media.

    Really a shame.

  3. Arbee says:

    First off, I hope the discs in question made it to someone who knows what they’re doing. Be that CHM/Bitsavers or Jason Scott or anyone else.

    Just for reference, you can’t read double-density 3.5″ Mac or Apple II disks on a PC with a standard 765 or similar controller. Apple used a variable-speed mechanism that split the disc into 4 rotation-speed zones to get 800k on a disk where PCs only had 720. A Catweasel or Kryoflux can get around the problem, but it’s not difficult to pick up a working vintage Mac on eBay that can read/write both double-density and high-density floppies. (For high-density Apple used the same MFM 1.44MB physical format as PCs, which greatly simplified data interchange. The controller was almost always an ASIC-ized evolution of Wozniak’s 1976 original Disk II controller instead of anything remotely like what PCs used though).

    Regarding emulators letting guest software access the real physical FDC, a lot of PCs don’t have one anymore (the machine I’m typing this on has USB 3.0 ports but no FDC), and of course there are a lot of security implications to that are probably better left alone.

  4. Michal Necasek says:

    Interesting. Commodore’s 1541 3.5″ drive packed 800K onto a DD floppy without any trickery, just using 10 sectors per track IIRC. The Amiga used even higher capacity (880K), but that was not a PC compatible format.

    You’re right of course that most modern motherboards don’t even have a floppy controller. And while USB floppy drives are available, those do not support the kind of low-level access that backup software may need.

  5. Michal Necasek says:

    I wouldn’t blame the “PC DOS 7.01” thing on them – there are some sites that refer to PC DOS 2000 as 7.01 out there. To be honest, 7.01 is the best shorthand reference 🙂 Or should it really be 7.00.1? Or 7.0r1?

  6. dosfan says:

    DOS 7.01 would mean that the minor version number changed and it did not in PC DOS 2000. Only the revision number (the value returned in DL for INT 21h function 3306h) changed. In fact I believe this is the only difference in IBMDOS.COM between PC DOS 7.0 and PC DOS 2000. I guess referring to PC DOS 2000 as “7.00.1” would be OK since IBM actually did that with PC DOS 5.00.1 though I don’t think they changed the actual DOS revision number.

  7. bills says:

    I can’t help but think it would have taken me 20 minutes to read these disks. Back when I worked in computer repair a couple of times I had to bring my Powermac 7600 or one of my old DOS machines into the shop to read disks for customers that have long since gotten rid of their old machines. I was the only one there at the shop that had ANY experience with older machines and I was the youngest one working there…

  8. Richard Wells says:

    I am more amazed by how many disks are still readable even as age takes its toll and all the new development methods discard support for little used features. Inertia is a powerful force.

  9. DOS says:

    Thanks, I love the site, very interesting and – in this case – useful: I forgot that Central Point Backup used its own disk format and I probably would have tried to use ‘dd’ to image the disks and then restore them using CPBACKUP in a VM myself! I wonder if I can run CPBACKUP in DOSEMU set up for direct hardware access, or if I have to use actual DOS..

  10. Richard Wells says:

    DOS: Try it yourself and report your results. I suspect in some cases cost cutting on the floppy drive will prevent reading diskettes with special formats no matter what OS is used. Some of the more recent internal floppy drives only work with 1.44MB disks; double density, extra tracks, or specialized sector layouts will not work. Yeah, limited like USB floppy drives but with a 34-pin connector on the back.

    I had more than enough problems with floppy backup software doing restores on a different machine back 20 years ago with real hardware and the same operating system to expect flawless reading with modern systems and virtual machine software interfaces.

  11. DOS says:

    No success with DOSEMU – is asking for direct floppy access as a new feature, so I guess it’s not there now. I could see the message in the root directory telling me it’s a CPBACKUP disk when I did an ‘mdir’ on it, though, so at least one of the disks has a few good sectors left!

    I wasn’t aware of the limitations of more modern floppy drives, I’ve only put 1.44MB disks in them! As for all my backups, they are on 1.2MB disks, and I don’t suppose there is such a thing as a modern 5.25″ floppy drive, but I certainly have a few old ones here!

    Looks like I’ll have to install DOS..

  12. Michal Necasek says:

    The limitation is technically speaking never in the drives… it may be in floppy controllers and certainly in software. For example, newer motherboards may not have any support for 5.25″ drives even though 3.5″ drives are supported (BIOS limitation). USB floppy drives are somewhat limited by the software protocol. Windows XP and later has very stripped down support for 5.25″ drives (such as no direct formatting support), and so on.

    So yeah, you may need DOS and a sufficiently old motherboard/BIOS.

  13. Richard Wells says:

    Look at some of the more recent Samsung 3.5″ floppy disk drives. They will only work with 1.44MB floppies no matter how old the system is. Surprised me when I used one to replace the gummed up original on a Pentium box as disks I could read on multiple old drives could not be read on the newer floppy drive. BIOS support does not help without drive support.

    Making this change didn’t make any sense to me. The cost of modifying the design has to exceed the tiny savings per drive.

  14. Michal Necasek says:

    That’s 1.44MB floppies as opposed to what? 720K? Or something like XDF disks? I can see how they could break DD floppies (250Kbps transfer rate). I don’t see how they could break any 500Kbps formats as the drive is too dumb a device for that.

    Maybe they just removed the density sensor? That would certainly do it…

  15. Richard Wells says:

    Removed density switch according to others that opened similar drives. But yes the disks I ran into problems with were 1.44MB XDF so there must be some other form of sanity check in these specific drives. Also tried a diskette that included extra tracks which didn’t work. Unfortunately, I can’t point you at confirming information because Samsung no longer has web pages devoted to floppy support and the few websites have early manuals which showcase the ability to use double density diskettes.

  16. Michal Necasek says:

    Extra tracks could be a mechanical issue… I don’t know if the drive would track the current position. But inability to read XDF media is really mysterious because the drive just provides analog data to the FDC. Samsung must have done something really “creative” there.

    I’ve been avoiding Samsung parts for a while now, after a bad experience with their hard drives. This isn’t really changing my opinion of Samsung 😉

  17. Jim Leonard says:

    I was surprised they had contacted me regarding information about how to run the software, but then neglected to ask me for copies of the DOS version I used (or any DOS version). I certainly would have gladly sent them a copy…

  18. Brian Taylor says:

    I’m even more surprised that they were familiar with linux allegedly, but didn’t just write protect the disks and then cat /dev/xxx > ~/floppyNN.img so that they weren’t working on the original media…

  19. LocalH says:

    @Michal I apologize for the late reply, but the pedant in me wants to correct one minor point from your earlier comment. The 1541 was Commodore’s 5.25″ drive for the 64/128, with a capacity of 174,848 bytes. It was the 1581 that accepted 3.5″ floppies with 800KB capacity. The drives I always wanted were the CMD 3.5″ drives, with HD (1600KB) and ED (3200KB) support, plus standard 800KB 1581 compatibility.

  20. Michal Necasek says:

    The funny thing about this blog is that sometimes relevant replies show up a year or two later 🙂

    Anyway, thanks for the correction. I should know better, given that I used to use a 1581 drive myself.

  21. MiaM says:

    The 1541 only had 170k capacity, using single sided double density 5,25″ disk and oly using 35 tracks, using GCR. Instead of Apples 3,5″ drives changing rotation speed, the 1541 (and all other commodore 8-bit 5,25″ drives) change the data rate. As the specification for the 3,5″ disks originally only had 35 tracks the hardware only had data rates suitable for the outermost 35 tracks without overriding the specifications of the disk media. You could usually cut out a “write enabled” jack on the opposite side of the disk and insert it upside down to use both sides (the index hole were not used by the drive) but some disks (ironically for example the swedish Commomodore importers own “PET” branded disks) didn’t like rotating backwards.

    Other drives like the 1571 used both sides, and for the (older and) bigger PET/CBM machines there were 80 track double sided drives that had larger capacity.

    Maybe you are refering to Commodore 1581, the only 3,5″ drive for Commodore 8-bit machines?

    Amiga had 880k on “720k” disks, afaik mainly because there were far less headers between the sectors.

    Amigas disk controller can read Mac 800k disks (with third party software), but you need a MAC disk drive. This is due to Amigas disk controller were designed for both CGR and MFM, but not with Mac compatibility as the reason for this but instead for Apple II compatibility 🙂

    P.S. Amigas disk controller can also read the old Commodore 1541 disks if you use third party software and a 5,25″ drive where you could adjust the rotation speed down from 300 to 280 rpm. (The software also includes an rpm meter program, it simply measures the index pulse rate from the drive). I’ve successfully tried that with one of those old Tandon full height 5,25″ drives that were used in the original IBM PC and XP.

    Of course the controller is also capable of reading and writing PC formatted disks. However if you don’t have at least version 2 of the operating system you either need third party software (Crossdos, which eventually were included in version 2 of AmigaOS) or you need a 5,25″ 360k drive as third drive (second external on A500, A1000, first external on A2000 as A2000 has room for two internal drives). I can’t imagine why the included software in older versions of the OS had a program to transfer files to/from PC formatted disks but it was hard coded to use the third drive and afaik also to 360k disks.

  22. Michal Necasek says:

    Yes, as mentioned in the previous comments, the reference was to the 1581 drive, from my experience both very nice and very not nice.

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