Floppy disk image formats supported by Virtual PC and Virtual Server

Floppy disk image formats supported by Virtual PC and Virtual Server

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Virtual PC and Virtual Server allow you to create and use 1.44MB (high density 3.5" media) and 720KB (double density 3.5" media) floppy disk images.  However they also support a number of other formats.  The supported formats are as follows:

Size: 360KB
Format: Single-density
Media type: 3.5"
Information: You probably are unfamiliar with this format.  The only place that I've ever seen this used is on the old Apple Macintosh installation media.

Size: 720KB
Format: Double-density
Media type: 3.5"
Information: This is the standard "old" 3.5" floppy disk format.

Size: 1.2MB
Format: High-density
Media type: 5.25"
Information: This is the largest standard format that was supported on the old, flexible, 5.25" floppy disks.

Size: 1.44MB
Format: High-density
Media type: 3.5"
Information: For people who are still using floppy disks, this is probably what they're using.

Size: 1.68MB
Format: High-density - DMF
Media type: 3.5"
Information: DMF, or Distribution Media Format, was a format used by Microsoft to allow them to cram more data on to a standard floppy disk.  It was used for the installation media for things like DOS, Windows 3.11 and Office 4.2.

Size: 1.72MB
Format: High-density - XDF
Media type: 3.5"
Information: XDF, or eXtended Density Format, was IBM's equivalent to DMF.  It was used for OS/2 and PC-DOS.  Interestingly enough it is not physically possible to read a XDF formatted floppy under Windows at all, so we only support the use of XDF floppy disk images (not physical disks).

You may come across floppy disk images that are already in these formats, in which case they will just work.  Or you can make your own floppy disk images in these formats by using tools like WinImage (http://www.winimage.com).


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  • Didn't the Connectix version support 5.25" floppies as well? I remember we had a test box with an old 5 1/4 drive in it for verifying this. Wonder if it still works. :)

  • 360 KB floppy disks were 5.25" in size, and I used them on the PC (before 1.2 MB ones came along):


  • >Size: 360KB

    >Format: Single-density

    >Media type: 3.5"

    >Information: You probably are unfamiliar with this format...

    Epson sold in the '80s a PC called the "QX-11". As far as I know, it was only sold in Latin America and -- at least in Venezuela -- marketed under the name "Abacus" as a bundle with some very impressive (if crash-prone) productivity software with a Spanish UI, apparently custom written in-house.

    The machine was really something. It had an 8086-2 8Mhz processor, an impressive high-resolution monochrome display at 640x400 (fully graphic!) with text sharp-as-knife; a sound chip with 3-channels (sound tones) + 1 ("noise") with 16 independent volume levels; two Atari-2600 joystick ports (!), a battery-backed RT clock and DOS 2.11 in ROM (fast, floppy-less boot!) as well as support for custom ROM cartridges that I never saw anything take advantage of. The box was about 3"x10"x12".

    The Abacus software featured always-active WYSIWYG bold/italics/underline display, drop-down menus and mouse support; there was a bitmap drawing program that could be driven with a mouse or a joystick and a spreadsheet with charting that could save to the same drawing format. The Word processor had on-the-fly text justification, customizable tab-stops and margins that could change anywhere in the document and embeddable images... all this while my peers were using WordStar! I'm not making this up.

    Anyway, the QX-11 also came with either one or two 360KB 3-1/4" single-density floppy drives. This provided a logical format that all DOS software could deal with, in a physical package that was more people-friendly than a 5-1/4" cardboard envelope.

    The only other machine I ever found that could at least read the oddball format was an 80286 clone I bought afterward. Everything else could only see the first track.

    (I'd love to get more info on the QX-11, but the Internet has virtually no data on it. A consumer PC with features then virtually unheard-of on anything but a Mac, I don't know why the QX-11 suffered a market fate that would make even Amiga fans feel sorry)

  • >Anyway, the QX-11 also came with either one or two 360KB 3-1/4" single-density floppy drives.

    I meant 3-1/2", of course. Sorry!

    (Now that I think about it, the charting might have been separate from the spreadsheet. Some of the other details might also be a bit off since I haven't used the machine in 15 years)

  • Pretty sure the DMF format started with Win95.

  • 360K format would most like really be the low-density 5.25" floppy that shipped with the original PC (1981).

    The original 3.5" Mac format floppies were 400K (not 360K) and used GCR encoding [1].  This encoding scheme can not be read by the floppy controller chip used in almost all PCs.  PC floppies (and the Trash-80) use MFM encoding.

    According to the Wikipedia article [2] on "floppy disk", there is no 3.5" 360K format.  There was, however, a 3" disk that held 360K, but it was not widely used in the USA.

    [1] http://en.wikipedia.org/wiki/Group_Code_Recording

    [2] http://en.wikipedia.org/wiki/Floppy_disks

  • >According to the Wikipedia article [2] on "floppy disk", there is no 3.5" 360K format.

    That's sort-of correct; as far as I know, there were no disks sold with those specs. The QX-11 used ordinary 720KB floppies.

    My understanding is that the drive skipped the odd-numbered tracks (so it used tracks 0, 2, 4, ... 78) for a total of 40 tracks and 9 sectors/track = 360KB.

  • I think there was a version of Office2000 on DMF disks - lots of them. Windows Installer (MSI) was specifically built to handle this kind of many-disk distribution, hence its strange handling of media, and reliance on volume labels.

  • Actually, most 5.25" floppy disks were formatted to 320kb (8 tracks) not 360kb (9 tracks) because earlier versions of DOS cannot handle the 9 track format (this is mentioned in the Wikipedia article).

    You are correct that the Macintosh floppies were formatted to 400kb - so maybe our low density format is just a nonstandard 5.25".

    RE: DMF - it was used for floppy installs of Windows 95, but it was also used long before then.



  • Actually, I have seen some non-dos machines that do use 360k 3.5" floppies.

    It is a bizarre arrangement where the device treats a 3.5" floppy like a 5.25" drive...

    Nothing but evil lies down that road!

    Interestingly enough, I used to have a program for my AT that let me cram like 1.4 or 1.6mb per 1.2mb 5.25" diskette.  I can't remember what dirty little tricks it played, but I suspect they are similar to DMF.

    Dang those were they days.... I used to have an app that could crank down the refresh rate on dram so that the 8086 & 286 CPUs could spend more time running your app.  On the 8086, it could have some serious improvements of up to 10%... sort of an early overclocking...

    If you'll all excuse me, I gotta go spend some time with my old TS-1000 until the nostaligia wears off... now where did I leave that 16k expansion pack...

  • Seems that at present no virtualization software support 5.25" 160kb or 180kb single-sided disk images.

  • If anyone on here has seen my virtual 5 1/4" floppy disk notcher, please let me know.  I seen to have misplaced it the last time I was on here, and I need to virtually double the size of my virtual floppy.  ;)

    I'm suddenly having flashbacks to my TRASH 80 model 1, and I blame all of you for that!  If I can't sleep tonight, I know who to blame.

    Did someone say Amiga?  Ah, happy thoughts.

    Great discussion guys!

  • >> If anyone on here has seen my virtual 5 1/4" floppy disk notcher, please let me know. <<

    I've got it right here:  attrib -r floppy.img

  • I have a Microsoft Entertainment Pack Volume Two Windows Series Disk Format: High-Density (1.2 MB)Version 1.0

    Dated 1990 and many more games and stuff from the 80s where could I find a site that could tell me more about them if you could help it I'm looking to sell all I dont have much need for them any more you may email me at allerbmik@gmail.com Thanks

  • What about the 320K diskettes of DOS 1.0 and 1.1?

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