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I've read many times that USB floppy drives will not format (or read/write) 720K disks. But then I read several posts online where people say they have done it. Even with Windows 10 (which is what I'm using).

One instance said to use the following command at the DOS prompt:

format a: /f:720

When I did that, here is what I got:

format a: /f:720
Insert new disk for drive A:
and press ENTER when ready...
The type of the file system is RAW.
The new file system is FAT.
Formatting 720 KB
Parameters not supported by drive.
Format failed.

Just like the message said, the format failed.

The disk I'm using should be good but I cannot completely confirm. It's also the disk that only has the one hole. The cover says:

FUJI FILM
Micro Floppy Disk
MF2DD
Double Sided Double Density
135 TPI / 80 Tracks

Is this possible or am I going to have to do something else? I plan on swapping my Tandy 1000 EX's 5.25" drive with a 3.5" version and I'd like to transfer images over that way (sneaker-net).

Thanks

EDIT

I can't find the model number. But it was highly rated on Amazon and some people even said they used this exact drive to format 720K.

Here is where I bought it:

https://www.amazon.com/gp/product/B00RXEWOAA/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

The company is Chuanganzhuo.

EDIT 2

On Stephen Kitt's suggestion, I tried a standard "format a:" but it didn't work.

Insert new disk for drive A:
and press ENTER when ready...
The type of the file system is RAW.
The new file system is FAT.
Verifying 1.44M
Invalid media or Track 0 bad - disk unusable.
Format failed.
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  • 1
    "Parameters not supported by drive" sounds fairly definitive to me. Is 1.44mb not an option?
    – Tommy
    Feb 13, 2018 at 0:17
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    @Tommy I don't want to format 1.44MB. I want to format 720KB. 1.44MB is no problem.
    – cbmeeks
    Feb 13, 2018 at 12:05
  • @manassehkatz correct. The floppy disk itself should be good and only 720K max.
    – cbmeeks
    Feb 13, 2018 at 12:06
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    @cbmeeks I am skeptical of general statements like "USB floppy drives will not format (or read/write) 720K disks". There is nothing inherently about USB (a technology that can handle storage, serial & parallel ports, network, video, almost anything) being somehow unable to format a particular type of disk. There may be something about typical (or most, or possibly all) drives connected via USB that prevents 720K format, but a drive model # would sure help to diagnose.
    – manassehkatz-Moving 2 Codidact
    Feb 13, 2018 at 14:28
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    @manassehkatz there’s nothing inherent in USB that prevents floppy drives from supporting 720k floppies, but that support does have a cost in the drive electronics themselves, and market forces mean that 720k floppies aren’t supported in most drives, because all the market cares about is 1.44M disks. (The few retro users who do want 720k support don’t register.)
    – Stephen Kitt
    Feb 13, 2018 at 15:56

9 Answers 9

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There are some USB drives which support double-density disks and formats, but as you suspect, not all of them. It is still worth trying a plain

format a:

to see what it does — USB drives control formatting themselves, so this should do the right thing if it supports double-density disks. If you have a Linux system handy, you can determine your drives’ capabilities by querying it with ufiformat -i.

However since your intention is to use these disks to transfer files to and from a computer with a double-density drive, this approach is likely to be unreliable anyway. High-density and double-density disks use magnetic media with different coercivity, requiring different field strengths to write data; a double-density drive can’t reliably format or alter a disk that’s been written to by a high-density drive. All is not lost though: you should format your disks in the Tandy’s drive (when you get it), and check whether your USB drive can then read and write the disks (but keep some disks aside that will only ever be written to using the Tandy’s drive).

Note that the holes in disks’ cases don’t determine the formats one-for-one. A DD disk will always end up formatted in double-density, and a DD drive will always format in double-density. An HD drive can theoretically operate in both modes (and will do so automatically with a DD disk). An HD disk can be formatted as a DD in a HD drive, but as mentioned previously will be unreliable in a DD drive; an HD disk formatted as a DD in a DD drive will work fine. You can use DD disks as HD by drilling an extra hole but then you’re taking your chances with the magnetic support.

If your USB drive really doesn’t support DD disks, a nicer option for file-transfer might be a null-modem cable and LapLink or InterSrv on DOS 6. Another option, which is very convenient, could be to use a floppy emulator such as the HxC in the Tandy; or use a HD drive in the Tandy, if that’s supported...

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    Thanks. Unfortunately, I can't get a DOS on my Tandy as I have no software for it and DOS isn't built into ROM. I didn't really want to purchase a GoTek or similar (I actually like using floppies) but I may down the road. I just don't have the spending (play) money at the moment so I was trying to use what I actually have.
    – cbmeeks
    Feb 13, 2018 at 12:10
  • I thought 1.44MB drives used twice the data rate of 720K drives but the same track spacing.
    – supercat
    Feb 13, 2018 at 21:26
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    @supercat ah yes, double the sectors per track, but 80 tracks in both cases. The DD/HD incompatibility stems from the medium coercivity and magnetic field strengths, not the head size (that’s on 5.25” drives).
    – Stephen Kitt
    Feb 13, 2018 at 22:00
  • Right. It is my understanding that a 1.44MB drive can read/format/write a 720K disk just fine because the notch is covered (the capacity sensor I think it's called). Even taping a 1.44MB disk (capacity notch) should trick the drive into thinking it's 720K. But I wonder if these USB controllers have that built into them?
    – cbmeeks
    Feb 15, 2018 at 17:29
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    Some USB drives support 720K disks fine, others don’t :-(. Standard 1.44MB drives can read/write/format 720K disks, the problem is that the disks aren’t necessarily writable by DD drives afterwards (because the “signal” from the 1.44MB drives is too strong for the 720K drives to overwrite); that’s another issue though, solveable by being careful — keep one set of disks which are written by the HD drive, and another which are written by the DD drive.
    – Stephen Kitt
    Feb 15, 2018 at 18:12
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Note: As I don't have a computer with Windows 10, I do not know whether it helps there as well, but this worked for me on Windows 7.

I do have a Fuji USB floppy drive (Not sure if this is the same type, but read on). It worked well with 1.44M floppies, but did not work for 720k disks with the original driver. The following procedure made it work:

  • Go to Device Manager, select the drive
  • Select "Update driver"
  • Select "Search Computer"
  • Select "Choose from list"
  • Select "Show all devices" (first option in list)
  • Select "NEC Systems"
  • Select "NEC floppy disk drive" (or similar)
  • Install this driver

This driver enabled 720k disk handling on my Fuji Floppy drive (Note, starting from Windows 7, the FORMAT command will no longer accept the /F:720 parameter - You need to instead specify number of tracks and sectors yourself like

FORMAT A: /T:80 /N:9

The very same driver works fine with a cheap Chinese USB drive as well - So, I suspect it should work on quite a number of drive types.

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  • Is the disk formatted this way really a 720k disk? I mean, just because you put only 9 sectors on a track to reduce the capacity must not change the bit rate. Did you try this disk on a system that can't handle HD disks?
    – the busybee
    Sep 30, 2019 at 8:31
  • @thebusybee Of course. Disks formatted that way run perfectly fine with an Atari ST or SInclair QL.
    – tofro
    Sep 30, 2019 at 9:53
  • Great, that's good to know! OTH that means that probably we can't get some arbitrarily changed formats just by giving "strange" parameters. :-( My hacker soul whines. ;-)
    – the busybee
    Sep 30, 2019 at 11:23
  • The /F switch was neutered starting with Windows XP, not 7 - the last Windows NT version to support using /F to format non-1440-KiB floppies was Windows 2000. (DOS-based versions of Windows continued to support a functional /F switch all the way through Windows ME [the very last DOS-based Windows version].)
    – Vikki
    Mar 31, 2020 at 17:45
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I found that more recent versions of Windows no longer support the /F: parameter. However, (with internal floppy drives at least) I've been able to format 720K with /T:80 /N:9 for 80 tracks and 9 sectors.

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This will work with the USB floppy drive you have mentioned, a Chuanganzhuo one, using Windows 10. You have to use a proper Double Density floppy disk, not a High Density one.

I tried it with a High Density floppy disk and it gave me Parameters not supported by drive.

C:\Users\J>format a: /T:80 /N:9
Insert new disk for drive A:
and press ENTER when ready...
The type of the file system is FAT.
Formatting 720 KB
Parameters not supported by drive.
Format failed.

So then I tried with a Double Density floppy and I got:

C:\Users\J>format a: /T:80 /N:9
Insert new disk for drive A:
and press ENTER when ready...
The type of the file system is FAT.
Verifying 720 KB
Initializing the File Allocation Table (FAT)...
Volume label (11 characters, ENTER for none)? CREATOR
 Format complete.
     713.0 KB total disk space.
     713.0 KB are available.

        1,024 bytes in each allocation unit.
           713 allocation units available on disk.

           12 bits in each FAT entry.

Volume Serial Number is 040B-DA30

I am lucky enough to have a DD floppy lying about, not everyone is. On the off chance someone Googles this in future, here is the answer...in my case I am transferring files from a PC over to an Atari ST and I can confirm that this worked with the Atari and that the disk was also writeable in the Atari drive.

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I successfully formated 720K on win10 by respecting the two conditions:

  1. only some chipsets (in the USB drive) support 720K, usually older chipsets
  2. the drive must detect the floppy as a 720K

Point 2 is sometime an issue if you use 1.44 floppy disks. I only have those so I usually put a paper to hide the hole in the floppy cases indicating the 1.44 MB format. But, some drive refused to format them and the format command gave me the diagnostic: Parameters not supported by drive..

This was a lie. The truth is that the drive detected the floppy as 1.44 MB even though I covered the floppy hole. The reason is that the drive uses a led and a photodiode to check if the hole is present. If the paper used to cover the hole is not dark enough, a small amount of light pass through and the floppy is reported as 1.44 MB. I successfully formated the very same floppy on these drives by using a black marker pen and darkening the paper used to cover the hole.

I only did full format of the disks. I was able to use these formated disks to transfer data from my Win10 PC to my Atari 1040 which has a real ~720K disk drive (the Atari floppy format is larger than 720K but the Atari can read 720K)

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  • Back in the day, when you bought a box of HD 1.44mb floppy disks they came with a small packet of (black) re-usable sticky tabs, which you had to use to cover the read/write notch in the disk casing, a hole which - if not covered - allowed the disk to be written to. You had to cover the hole to make a disk read-only. These were always black, absolutely impervious to light, because otherwise the beam emitted by the light-emitting diode would leak thru the hole and reach the detector, allowing the drive to write to your supposedly un-eraseable floppy!
    – Ed999
    May 6, 2020 at 14:19
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The only way I could use a batch of unused 720k disks, designated as '3.5" - 2D, 135TPI, Double Sided, Double Density, 1MB (720K)' was to use a FULL format, not a Quick format. This took 11.5 minutes for each disk! On checking the properties, the capacity was given as 1,457,664 bytes, 1.38MB, but the free space was shown as 799,744 bytes, 781KB, and the used space was shown as 657,920 bytes, 642KB. This was under Windows 10, build 1803. If it is imperative to use these disks, then it's a possible solution, but not very quick or practical.

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  • 3
    11.5 minutes for a full format sounds like it attempts to format every track several times, probably because it gets errors during verification. Which seems to indicate your are trying to format a DD disk in a drive that's only made for HD disks. Even if the format succeeds eventually, the disks will be unstable, and you'll quickly get read and write errors. That may be enough to transfer data, but don't count on storing anything on those disks for a longer time.
    – dirkt
    Jun 9, 2018 at 12:44
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I worked for a commercial reseller of similar machines back in the early 90s.

The combination of BIOS and DOS of those machines at the time did not recognise/support formatting in 720KB, but the hardware/DOS was able to use those formats after the diskettes were formatted on those new formats.

At the time, I wrote a routine for formating 720KB diskettes in assembly or C using BIOS calls (can't remember). My employer was more than happy pre-formatting diskette boxes for customers and charging a small additional fee.

I suspect also @BrianKnoblauch idea of format with /T:80 /N:9 might work, if max capacity checking does not get in the way.

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Get a used IBM usb Floppy drive from ebay. Tested year 2003 and 2009 version MPF82E. Both of them can read/write/format 720k disks. Works with windows 10 1803 and windows 7/xp.

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try it! Find the square hole that does not have a slider. (Circled in the above pictures). Take a short length of tape, (3-4cm or 1 1/2inchs long), and cover both sides of the hole.

The reason this works, is that there is no physical difference between 1.44MB floppy disks and 720K disks, except that the 720K disk is missing the hole that you just covered. 

Format A: /T:80 /N:9

its work on XP

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  • 1
    Some 720K floppies are made with lower-quality tape, which won't store high-density data as well. More to the point, this question is asking how to format a floppy as 720K, not how to format a 720k floppy as 1.44M. Please read How to Answer.
    – wizzwizz4 ♦
    Oct 26, 2019 at 9:43
  • Brian, I'm baffled by your reference to (Circled in the above pictures) as your answer doesn't contain any images! Ultimately, the only reliable way to format a DD disk is to use a DD drive to do so. No amount of cheating will allow a disk formatted in some other way to be written or read reliably in a DD drive.
    – Ed999
    May 6, 2020 at 14:28

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