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Preserving a floppy disk with a logic analyzer and a serial cable:
Being involved with retro computers, I have a few floppy disks (of the 3.5-inch variety) that I would like to preserve as faithfully as possible. Of course, I know there are dedicated devices for doing that, such as the Kryoflux or the SuperCard Pro. But it occurred to me that I already own the required hardware to capture the low-level data from a floppy disk: my Saleae Logic 8 logic analyzer.
Side note: While I can only highly recommend the Saleae analyzers for their features and easy-to-use software, the things described here can also be done with other logic analyzers – including those available for less than 10 € from your favorite Chinese online store – and using, for example, the free Sigrok software.
Contrary to more modern mass storage devices such as ATA hard drives or USB sticks, the interface to a floppy drive is much more low-level. E.g., you can ask a modern hard drive to read sector 1337 and it will return you the bytes stored in that sector. In contrast, as soon as it is selected for reading and the disk is rotating, a floppy drive will simply give you a pulse each time the magnetic flux changes, i.e. whenever the magnetic field changes orientation. It is important to know that the magnetic field orientation does not directly represent the individual bits that are stored on the disk. Instead, an encoding scheme is always used. The details of the encoding differ between systems – which is why you cannot read an Amiga disk in an Atari ST, for example. Regardless of the implementation, the encoding always needs to take care of several things: 1. Encode the data bits, obviously. 2. Clock recovery. This is essential because different drives may rotate at slightly different speeds and the floppy disk controller thus needs to determine the actual data rate. 3. Marking the start of a sector. This is often achieved by flux patterns that do not occur in regular data.
Raise your hand if you remember storing data on a floppy disk. Or was that on a floppy disc?
(Score: -1, Troll) by Anonymous Coward on Sunday January 30 2022, @05:31PM (3 children)
Of course the International Jew would want to steal the bits from everything, and old floppies are no exception. Then they turn around bitching and moaning that poor home users are pirating the software their Jew buddies entrenched in government insist on forcing on their users.
It's a lot like Metallica bitching about piracy and getting Napster shut down, after they themselves bragged about "crashing on couches" and "copying tapes all night." Lars Ulrich was the one making their business decisions, and he is an International Jew. Not as Jewey as KISS, but still pretty goddamn Jewed.
(Score: 2, Funny) by Anonymous Coward on Sunday January 30 2022, @05:42PM (1 child)
How the fuck did this get modded up?
It is probably the work of the International Caucasian.
(Score: 0) by Anonymous Coward on Sunday January 30 2022, @06:01PM
It is the work of the International Incel, sitting in his basement and whining his head off about How Unfair It All Is and how entitled he is.
(Score: 2) by epitaxial on Monday January 31 2022, @04:01AM
You can always tell an autist at work. They love repetition so much they will post the same inane garbage day in and day out.
(Score: 1) by crm114 on Sunday January 30 2022, @05:44PM (5 children)
First computer was a home built Digital Group kit, with a cassette deck.
When we could afford it we got dual 8" floppy drives.
5.25" floppies from there, and on to 3.5" - although they weren't "floppy".
Remember zip drives? That was a very short lived "thing"
(Score: 0) by Anonymous Coward on Sunday January 30 2022, @08:25PM
Zip drive's bigger brother the Jaz disk at 1GB. I remember using Jaz drives to courier large amounts of data across town. At the time, the transfer speed of a Jaz disk doing 60mph down the highway was faster than uploading between branch offices.
I have a lot of memories of Jaz drives.
(Score: 1, Touché) by Anonymous Coward on Sunday January 30 2022, @10:39PM
When I ordered my first PC I wanted an LS120 drive but got told I should have a Zip drive instead because they were more reliable. I stopped using the Zip drive because it was really unreliable!
(Score: 5, Interesting) by Dr Spin on Sunday January 30 2022, @11:18PM
Later, I did a hard disk controller with programmable logic to recognise the address marks that indicate start of the address or data of each sector.
when I did this, I discovered that IBM had messed up the address mark. If you looked for a data pattern that had a single transition between two gaps that were one clock cycle longer than the longest one permitted in normal data, then you got far less faulty sectors than if you used IBM's version, which was clearly meant to be this, but failed because someone, somewhere, had described the clock pulses high end first, but the data pulses low end first!
My data separator could be jumper configured to use IBM address marks or mine!
The original design was MFM, but I later did a GCR version which gave about 60% more capacity from the same drive - and all with the higher reliability of my address marks.
The company made millions because they bundled a BBC micro and hard disk with software to print labels for pharmacies (which a new law required to be printed, not hand written) - this needed a database of all known pharmaceuticals and permissible dosages - which would not fit on a floppy, and a PDP11 cost a lot more than a BBC micro with a hard disk. (My PDP11/70 used about 20kW, a BBC micro was less than 100W).
Warning: Opening your mouth may invalidate your brain!
(Score: 2, Interesting) by aixylinux on Monday January 31 2022, @01:38AM
I first encountered a floppy disk (8" version) on an IBM System/370-158, which used it to load the microcode. A Customer (hardware) Engineer installed a EC (Engineering Change) and all he brought was the floppy. We had to do a power-on-reset. I remember the clickity clack as it bootstrapped itself from the floppy. Later, if we had a power failure (no UPS), it would bootstrap again before we would have an operational console and could IPL (boot up) from the hard disk.
I later worked on a DEC PDP-8 which was upgraded from paper tape I/O to dual 5.25" floppies. I wrote a device driver for it that would pack more data on the disk than DEC had envisioned.
(Score: 1, Interesting) by Anonymous Coward on Monday January 31 2022, @08:13AM
I actually used to have a SCSI Zip drive has the main spindle for a NeWS Unix/NetBSD workstation...
While the read/write throughput wasn't outstanding, BSD Unix was actually designed with slow I/O in mind, and the system was actually very usable-- Emacs, Kernel compiles, a 25MHz MIPS box living life to the fullest...
(Score: 2, Informative) by Anonymous Coward on Sunday January 30 2022, @05:45PM (5 children)
Fancy IBM PC disk drives could write to both sides of the 5.25 inch floppy disk.
For the Apple and Commodore, you had to flip the new disk over and use a hole punch to make another notch on the side. It was like using a vinyl record. Use Side A. Flip over. Use Side B.
(Score: 4, Informative) by SomeGuy on Sunday January 30 2022, @07:04PM (3 children)
Actually, the very original IBM PC model 5150 shipped with single sided drives. But the controllers supported double sided, so as soon as double sided drives were available, everyone threw out the single sided drives and installed double sided drives. There were a small few IBM PC titles that used Flippy disks for compatiblity.
In contrast, the very last Apple II 5.25" drive manufactured and shipped with the Apple II GS was still single sided.
(Score: 2) by Magic Oddball on Monday January 31 2022, @03:16AM (1 child)
The Apple IIgs was shipped with an 800k 3.5" disk drive, and all software/games written for the system was released on 3.5" disks. Apple sold an optional 5.25" drive in the GS 'platinum' color scheme simply so people could take advantage of the GS' ability to natively work with the older Apple II disks, which is why it was single-sided.
(Score: 2) by SomeGuy on Monday January 31 2022, @06:38PM
All of the IIGSes I saw in use back in the day had both 3.5" and 5.25" drives - and little or no 3.5" software with them. They were used as glorified IIe machines.
You missed the point that all Apple would have needed to do was add a simple head select line, and patch AppleSoft DOS/Prodos to support it. It would have remained fully backwards compatible. Logically, double sided support should have been added at least at the time the IIe was introduced.
Some third parties tried to build double sided drives like that (even quad density), but they never caught on because Apple controlled AppleSoft DOS/Prodos and would never include support.
(Score: 0) by Anonymous Coward on Monday January 31 2022, @03:17AM
The //gs was still using single sided 5.25" disks because the main reason for having the 5.25" drive was for compatibility with older software, which was already on single-sided disks. Software for the //gs came on 3.5" disks, which were double sided (and held 800k like the Mac, not 720k like the PC).
Later models of //e and //c also came with 3.5" drives, but the sector interleave was different from the //gs. They could read each other's disks, but very slowly. The //gs did its decoding in software, while the others used an on-drive CPU to do it. This was true even once the //c got a 4MHz CPU, which was faster than the one in the //gs.
Apple made a "Superdrive" for the //gs (and could be used with the //e), which could read both Apple // formats, Mac, and PC disks, including both 720k and 1.44MB. It was the same mechanism as the 1.44MB Mac floppy, but with fancier electronics. They were always rare, and are expensive today.
(Score: 0) by Anonymous Coward on Monday January 31 2022, @02:27AM
I remember doing that. Commodore used a custom higher density format where the outer tracks had more sectors than the inner tracks, like modern hard drives do. Too bad they crippled the whole system with their crappy serial port.
(Score: 2) by Snospar on Sunday January 30 2022, @05:47PM (2 children)
I remember compiling custom kernels that would fit on a single floppy with enough simple tools that I could (hopefully) rescue a borked machine. Just checked and my current kernel is almost 10MB, I don't think it would be easy shrinking that down by 90%. It's been so long since I needed to build a custom kernel I probably wouldn't even recognise half the options - so much fun when you turn off the wrong essential features.
Huge thanks to all the Soylent volunteers without whom this community (and this post) would not be possible.
(Score: 1, Interesting) by Anonymous Coward on Sunday January 30 2022, @05:53PM
It's actually not changed much since my first kernel build nearly 20 years ago. a lot of the growth has been in supporting non-x86 architectures...
(Score: 2) by choose another one on Sunday January 30 2022, @07:07PM
Used to do this for turning Windows boxes into X terminals (without paying $$$). Some of us worked using DOS/Windows in the lab, some of us preferred Unix but didn't have the budget for Unix boxen.
I managed to get enough on a 5.25 floppy (which was all some of the machines had) to get Linux booted and able to NFS-mount a (read-only) filesystem with everything else from the main Unix cluster (couldn't use the hard drives on the PCs as they were used for DOS/Windows and had Windows users' stuff on), from there you could run stuff direct on Linux or just use the box as an X terminal to make use of shared Unix machines elsewhere in the building. I recall it was quite tricky to get it that small, even back then. Most distros I think were 3.5in floppies with 1 1.44M boot and then separate 1.44M root (plus another couple of boxes of disks for the rest, if offline and using sneakernet not nfs).
In many ways Linux (kernel) wasn't that small back then either - 1MB was actually quite a lot, Emacs at the time was lambasted for being "eight megs and constantly swapping" and our standard (undergrad) storage quotas on the Unix system was 4 Meg (just like back in BOFH #1, except it was few years before).
(Score: 2) by mcgrew on Sunday January 30 2022, @06:02PM (2 children)
Better is to still have a floppy drive laying around somewhere. There's an old computer in my basement with one. Now if I could somehow read a five inch Apple IIe drive...
Carbon, The only element in the known universe to ever gain sentience
(Score: 4, Informative) by Immerman on Sunday January 30 2022, @06:20PM
Yep, I've got a couple USB floppy drives, just in case. I think it's been a couple years since I actually used them, but every now and then they come in handy.
I actually recently learned that 3.5" USB floppy drives are still available that read at up to 4x the normal speed - but almost nobody actually mentions the fact, so you've got to look up a list of fast models. Just thought I'd throw that out there in case anyone has an archiving project in their future.
(Score: 2) by bzipitidoo on Monday January 31 2022, @04:45PM
Need to use the drive once in a while. 25 years is enough time for belts to stiffen and set, dust to build up and clog things, and lubrication to settle and pool and partly evaporate, and thicken. Of course it should be stored in a manner that keeps the dust out, like in an air tight container.
A few weeks ago, I tried using some of my old 3.5" floppies again. Only one of my 4 floppy drives worked at all. Two may still be working, but one is a parallel port interface for a nettop computer that had its hard drive fail. That drive may still work, but it is specific to that machine, and as far as I know, can't be used elsewhere. The other that may still work is a combo 3.5" and 5.25", but seems many of the last motherboards that support floppies only support 3.5", so I couldn't use that drive either. The drive that mostly worked consistently failed to read the last few tracks. Was the problem the disks, or the drive? Maybe some external magnetic field corrupted the outermost parts of the floppy disks? Or maybe the drive arm wasn't moving quite right and was not able to reach the last tracks?
I got a USB floppy drive, and ran into another gotcha. That drive will not read double density floppies, it will only read high density.
(Score: 5, Interesting) by gznork26 on Sunday January 30 2022, @06:07PM (2 children)
The first computer I touched was a desk-size wonder called a DIGIAC 3080 that my high school had gotten. Flip the bat switches to set the first few memory addresses in binary to tell it to read a punched mylar tape containing the machine's assembler, so you could read a punched paper tape with your assembler-language program. The thing had a drum memory with 4,096 addresses.
So after working with punch cards in college and at work after that, finally having an Apple II+ with a floppy drive was satisfying. So much space!
(Score: 2) by hendrikboom on Sunday January 30 2022, @07:12PM
The drum machine I started on was a Bendix G-15.
(Score: 1) by Acabatag on Sunday January 30 2022, @08:29PM
That was the process I had to use to boot up FOCAL off mylar tape on the PDP-8 in the Science Building in College to complete my (Intro to) computer programming class.
(Score: 5, Interesting) by hendrikboom on Sunday January 30 2022, @07:15PM (1 child)
The Amiga actually read all the flux changes, and then the OS used software to turn the sequence of flux changes into the desired bits. The blitter that was designed for graphics made this fast.
The reverse was done on writing.
This meant that IBM PC floppies could be read and written by a change of software.
-- hendrik
(Score: 2, Interesting) by Anonymous Coward on Sunday January 30 2022, @07:26PM
Yep. The program I used was called messydos. Just to show how much better the 6800 series was, my 7 MHz Amiga running an emulator tested out as a 33 MHz 286 ms-dos machine.
(Score: 3, Interesting) by SomeGuy on Sunday January 30 2022, @07:16PM (1 child)
Using a logic analyzer to record the digital output is sort of re-inventing the wheel. Not that it doesn't need re-inventing sometimes. There are ups and downs to each available archival device. The kryoflux does a bit more than just record - it does some tricks to adjust for drive speed variation, and can write good quality flux dumps back to a physical disk.
What would be more impressive is bypassing the floppy drives digital electronics, and capturing the analog signal directly from the head. I seem to recall an article from a while back where someone did just that. With some serious signal post-processing that could be used to recover data that is otherwise unreadable.
(Score: 0) by Anonymous Coward on Sunday January 30 2022, @11:13PM
Millennials love to do things the hard way.
10 seconds per track and Python is so fsking stupid, but hey, they re-invented MFM decoding for the 1000th time.
(Score: 5, Funny) by Rosco P. Coltrane on Sunday January 30 2022, @10:09PM (4 children)
For people of my generation, cassettes and diskettes can burn in hell, and thank God for solid state memory. Yeah they remind me of my youth, but they sure don't bring back any fond memories of early personal computing.
To today's generation, diskettes are precious collectibles worth spending a lot of money preserving, or low-level copying - like if that had any added value whatsoever. Exactly like vinyls: I'll never understand how those hateful things are coming back to plague us once more, apart from the point of view of wanking in front of a lovingly curated collection of the damn things. I guess the time of diskette collection wanking has come...
(Score: 0) by Anonymous Coward on Sunday January 30 2022, @11:45PM
》 I'll never understand how those hateful things are coming back
Millennials were collectively dropped on their heads as babies and the damage was permanent.
(Score: 0) by Anonymous Coward on Monday January 31 2022, @03:31AM
I think it's like antique anything else, you either like it or you don't.
It's weird, whenever I pick up a 3.5" PC disk, it feels old and clunky, but a 3.5" Apple disk feels stylish and high tech. I guess it's the effect of wanting a //gs (and not getting one until decades later), but 3.5" floppies on PC were just ordinary.
(Score: 4, Insightful) by deimtee on Monday January 31 2022, @03:40AM
Blame the the egomaniacs who demand their track be the loudest, and the sound mixers who acquiesced, ie the "Loudness Wars".
CDs, and later MP3s, let them compress the dynamic range and push it all up to 11. The music sounds shit. You can't do that with vinyl, it just can't take it.
So the vinyl sounds better because the music is better, not the format.
No problem is insoluble, but at Ksp = 2.943×10−25 Mercury Sulphide comes close.
(Score: 0) by Anonymous Coward on Monday January 31 2022, @01:10PM
Devices today are just too complicated to REALLY understand how they work. The old devices are simple enough that you can tinker with and learn how they operate at a very deep level. I think that is an important reason. You simply can't do that with modern tech.
(Score: 1, Informative) by Anonymous Coward on Monday January 31 2022, @01:33AM (2 children)
Hard disks, floppy disks -- for the square things, use the K.
For the round things, like compact discs, use the rounded c -- disC.
(Score: 0) by Anonymous Coward on Monday January 31 2022, @03:26AM (1 child)
You're right about the usage, but I don't understand why the distinction exists.
(Score: 0) by Anonymous Coward on Monday January 31 2022, @03:38PM
Just be glad some manufacturer didn't start spelling it "disque."
(Score: 2) by MIRV888 on Monday January 31 2022, @04:23AM (1 child)
I was in 2nd grade and though it was completely bad#^&.
I knew pretty much from that point that computers would be my career.
The external 5.25 drive and modem cartridge for the Commodore 64 in 5th grade sealed the deal.
BBS's FTW
(Score: 2) by Dr Spin on Monday January 31 2022, @03:43PM
You would not say that if you had a TU79 tape drive on your home computer!
Making a backup of an RK07 or two onto a TU80 would give you hours of entertainment of an evening.
And you could play Colossal Cave while you did it.
Of course you might need ear defenders and a lot of money for the electric bill.
Warning: Opening your mouth may invalidate your brain!