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Comment by wkjagt | Hacker News Reader

I actually went through this yesterday! I opened a new (still in plastic!) box of HD “floppies” to make a bootable disk for my 486. I sent a picture of it to a friend and he replied “how big are these? 512k?”. I too thought it was common knowledge, the number 1.44 burned into my brain forever, but I do give my friend credit for being at least in the right ballpark, and also to come up with another number that has geek value.

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Also a good guess because if I remember correctly the floppy floppy disks which were flatter with a larger surface area and actually floppy were about 512k or so.

I only ever saw one machine with one of those in though and of course it was at school, running useless software for us

For PC I remember the 5.25" were 1.2MB. Not actually bad capacity comparatively. Or 612KB for single sided.

Though Wikipedia lists quite wide range of sizes none at 512KB.

Actually 5.25" were usually 360 KB, the 1.2MB came later, just like 3.5" floppies, they were originally 360 Kb, then 720KB, only later they became 1.44MB:

https://en.wikipedia.org/wiki/Floppy_disk#Sizes,_performance...

Though it all happened in a few years, when the 3.5 came out most if not all the 5.25 were already 1.2MB, and the first 3.5 were advertised for their robustness, not for their capacity (which was initially inferior).

For all the complaining I do about USB's naming standards—"Full Speed" is not in fact "full", it's slower than "High Speed"—I don't remember having the same gripes about Double Density vs. High Density :)

You skipped the time where there were punchers to open a second hole in 3.5 DD to make them HD (those were the times .... ;)):

https://www.webcommand.net/index.php/2019/07/31/does-anyone-...

I seem to recall that there was a dedicated word-processor machine by someone from the original Macintosh team that formatted 3.5" disks for 512K.

The first computer I bought was a 386. But I tried the used machine market before, to see if it was possible to save some money.

My father drove me to a company that had their used system for sale. It was embedded in a desk, the screen was minuscule.

I don't know what impressed me more: that when I asked (politely, looking for a reason to walk without offending the seller) how much memory it had, they started counting bytes included in the manual, or the 8'' floppies. Those were big.

single density floppies were 720k

Pretty sure thats double density, the bigger ones were HD for high density. You could usually format a good floppy for either if the cutouts were made.

There were basically never any 5.25" or 3.5" single-density disks on the PC, and the definition of double-density varied depending on disk size.

5.25" disks were 40 track, 9 sectors per track with 512 byte sectors for 180KB per side. For 3.5" disks, the definition was 80 track so 360KB per side.

High-density increased the number of sectors per track to 15 for 5.25" (600KB per side) and to 18 for 3.5" (720KB per side).

Except on a Mac, then they were 800k.

And 880k on Amiga.

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