I dug some ancient floppy disks out. * Memorex single sided, double density 5 1/4". There is no mention on the box of mb or kb, which is what I expected because back when I used these there was only talk about sectors (IIRC, it was 20+ years ago).
I checked eBay to see if this unopened box was worth anything (not really) and one listing indicated that 2S/HD was 1.2 MB. I’m guessing that HD is twice as big as 2D (double density), which would put these at about .3 MB.
I didn’t get much from wikipedia except for this nugget: “…40‑track double-density (360 KB)…”
This is really just for my own curiosity, but it’s something that I’ve been curious about for over 2 decades, since about the time I went from thinking about floppy disk capacity in terms of sectors (63, IIRC) to bytes. So, while we’re at it, how many bytes on a sector?
FWIW, the computer that I used for most of the 80s was a TRS-80 64k color computer.
(Long story, but I subbed for a science teacher today and will tomorrow and the lesson is on magnets and 50 minutes is a long time to just play with magnets so I’m going to go off on a tangent with the older kids.)
And back in the days of the Apple ][s, we’d have the entire operating system and a few games on one of those 360K babies.
Most of the single-sided ones would actually have magnetic media on both sides, with only one side tested to ensure quality control. You could use a hole punch to notch the place where the drive sensor checked for writability, and most of the time it would work as doublesided when you flipped it over. We were cheap like that.
Saltire, back in those days, were you well aware of how many kb the disks held? Because I don’t recall reading about bytes or KB in my Rainbow magazines or in the books that came with my co-co, nor is there anything on this box of disks (or is it discs?) mentioning capacity in bytes. Is this a PC vs. Mac thing? Or is it just that capacity wasn’t measured (or mentioned) in bytes until a certain time?
things back then were not uniform, things varied from computer manufacturer to manufacturer and would even change with and within models. you would format the disk for your computer before using. you got what your machine was intended to run.
Especially when it costs thruppence and sixpence just to get on the bus. (More if it’s an MCA bus, of course, but that’s after decimalisation, which is spelt “The fuck’s a tanner again?” in the States.)
It depended on what sort of computer you put them in, IIRC. TRS-80s had different capacities than C64s and both were different than Apple II computers.
(or Macs vs PCs vs Amigas a few years later with 3.5" diskettes)
So they’d just label them 5.25" SS/SD or whatever.
Right. In the same way that a hard drive might have different capacities depending on if you formatted it using FAT, NTFS or FAT32, floppy capacities varied a bit. Also, since you often had your OS on there (though there were certainly pure-data disks), the free space would vary depending on your OS version.
I knew the 360Kb number, and 1.44Mb for 3.5-inch disks, but didn’t pay too much attention. I’d just try to write something, and if I was told the disk was full I’d stick in a different disk.
Even when the world had moved on to 3.5" non-floppy floppies, OSes could still fiddle with the drive hardware enough to put, say, 1.722 MB of data on a supposedly 1.44 MB disk. tomsrtbt (pronounced “tom’s root boot”) does precisely that:
Virtually all 1.44 drives support 1.722 just fine, but it is possible for
an extended format to break a floppy drive, use tomsrtbt at your own risk.
As I recall, floppy drives could be misaligned slightly relative to each other; as long as you stuck with the standard formats, this usually wasn’t a problem, but stretching things with nonstandard ones risked making disks that could only be read successfully on one machine. Frankly, though, a bigger worry, especially as floppies began to give way to thumb drives and writable CD-ROMs, was the fact floppies were often unreliable regardless of formatting.
Good point. Other operating systems used other track formats that could put different amounts of data on the same medium.
For instance, the DSDD (Double Sided Double Density) 5 1/4" floppy everyone’s talking about (360K capacity under DOS and related OSs) was 440 Kbytes when formatted for an Amiga.
Of course, Amigas didn’t come with 5 1/4" drives, but they were available as an aftermarket accessory.
My son works for DeVry, and they have a bunch of Banker’s Boxes full of old floppies with sensitive information they no longer need to maintain. Of course, being a school of technology, they have some fancy shmancy super high tech gizmo to destroy the floppies…3 20 year old kids making minimum wage. They ripped, cracked, bent and flung their way through an entire box, and then realized they’d destroyed less than an iPad worth of memory.
