How to read and write old floppy disks

This Web page last updated dated Sept 30 2014

This page is about ways to read and write "old" floppy diskettes (disks from systems of the 1970's and 80's). On another Web page, I have a lot of information about floppy drives, diskette media, and various issues.

To contact me, or for ordering information follow this link. To return to my S-100 list click here.

"I want to read old diskettes on my PC/Windows/OSX/Linux machine"

Some people ask: "I want to read 5.25-inch or 8-inch diskettes on my PC/Windows/Linux machine. Please sell me a complete system, or tell me where to get one." Some people ask: "I have an 8-inch drive, sell me the power adapter and cable for use with my modern computer." Often they have no idea how this might be accomplished beyond those statements. Some people want to read CP/M oer other non-MS-DOS 5.25" or 3.5" diskettes, or old Mac 400K or 800K 3.5" Mac diskettes, on a Windows PC. A few people want to read really ODD formats - hard sectored, M2FM, and so on.

Folks, this is not a "plug and play" project. You can't just "plug in" something and it magically "works". Sorry.

In the 21st century, you have four choices to accomplish the above goals.

Choice one: contact a "data recovery service" and tell them everything you can find out, about the origins of those diskettes, including the programs and operating system(s) used to produce them. They will hand you the files for a fee, and for an additional fee may be able to "convert" the files for use with modern "applications" (software).

Choice two: Buy some special-purpose, privately produced, floppy drive interface for 3.5" or 5.25" floppy drives. This will be a PCI card which must be added inside a modern computer with PCI card slots. Or it may be a custom "microcontroller that supports or emulates floppy drives". (See all the notes below.) Add a cabling adapter to make 8-inch drive connections if you are working with 8-inch floppy drives as most "interfaces" don't support that connection. Use the software offered with the interface, which may or may not be able to "interpret" the data on the diskettes into files. YOu need to be a computer programmer and engineer to make this choice "work", and you may not be successful. ...and you still have to convert the file data, to something a modern program can "understand".

Choice three: get an older PC with an internal floppy controller, or an ISA-card floppy controller. Add that 8-inch adapter if desired, as noted above. Find and use some ancient PC software in MS-DOS to "handle" the odd format under program control. Or use Linux and its binary file tools, which won't produce "files". ...and you still have to convert the file data, to something a modern program can "read".

Choice four: get an even older PC with ISA slots, and find some ancient hardware and software that reads non-MS-DOS disk formats. Most of these were developed to "unlock" or "crack" copy-protected diskettes. Example: Copy II PC Deluxe Option Board. It's a special floppy controller which sits on an ISA slot card. Using the software, you can write and read Mac 800K disks. The manual for the product is "out there" on the internet. (Thanks to Gregory Robertson for this information.)

Neither solution two or three, lets you use the odd disks like "normal" MS-DOS diskettes, for example through Windows Explorer. (Some Linux solutions let you "mount" some diskette formats, some not.) The rest of this Web page, describes some of the options and hardware and software suggested above. A few odd things are described immediately below.

Note on 8-inch "adapters" or "cables for PCs" To read 8-inch floppy drives on a "PC", you MAY be able to connect 8-inch drives to a PC's internal floppy controller (if it has one). But you need an 8-inch drive, with power supply, in a cabinet; a 50-pin cable for the 8-inch drive; a wiring adapter for the 50-pin cable to your 34-pin floppy controller; and software and software knowledge! Even with that, MOST PC floppy controllers won't read old single-density format anyway! See this section for additional details; the rest of this page for more details.

Note on reading "disk formats": Reading non-MS-DOS disks on a PC, even with the right sized floppy drive "properly" connected, can be difficult. The floppy CONTROLLER on the PC, which does all the work of reading, writing, and formatting, may not be able to accept non-MS-DOS formats, even WITH software. Some early disk formats including Apple's, use odd bit patterns. The controller may not accept single-density. Or it can simply be a problem with knowing which of the MANY MANY CP/M or other disk formats you need to use with your particular diskettes.

I've now provided some general descriptions and "keywords", about "cabling" old floppy drives to a modern computer, "to read old floppy disks". You can use this information to find more information and increase your understanding, and if you wish to do this work yourself. Further notes on specifics I've mentioned are below and on other pages on my Web site.

discussions about converting from 8" and 5.25" drives to 3.5" drives

In Feb 2005 there were some discussions in popular newsgroups, about converting old CP/M systems from 8-inch and 5.25-inch floppy drives, to 3.5" drives and media. Issues raised included support of FM or single density; finding old media; choices of formats. I decided these discusssions were worth preserving, as these issues come up over and over. One discussion was in the Classic-comp CCTECH discussion. The other occurred in Usenet discussion group comp.os.cpm.

a good Web site for using 8-inch CP/M diskettes on PC's is my colleague David Dunfield's Web site. Check my discussion of Dunfield's disk site elsewhere on this page.

It can be a challenge to use 5.25-inch "quad density" drives on modern computers, or modern floppy drives on older computers. The Web page linked here describes how to adapt a Teac FD-55GFR 1.2M drive to use for 800K (96TPI) formatted diskettes. Other notes there may apply to other brands of 1.2M drives. Note that the Web page is copywrited by the author, the Web link is to a licensed copy of that work.

5.25-inch to 8-inch cabling adapters

8-inch drives use most of the same signals as 5.25 inch drives. So old PC floppy controllers, can be adapted to operate even older 8-inch floppy drives, by "adapting" signals from the 34-pin connector of the 5.25 inch drive, to the 50-pin connector of the 8-inch drive.

Some people build these 34-pin to 50-pin adapters, you could build one. The CP/M FAQ has a diagram; I've not checked it so no guarantees. Here's a copy of the description from the CP/M FAQ. Dave Dunfield's specific notes for attaching 8-inch drives to PC's are at at this Web page under "Notes on connecting 8 inch and external floppy drives".. You may find problems adapting this to specific drives, as some signals may be used differently. This is not a "plug and play" solution! No guarantees! That's why my Web site has all this information and references, OK?

If you want to buy such an adapter, look around the Web for persons or small companies who offer such a thing. Again - it is just wires, not a "controller" or a "magic cable that connects your PC to an old floppy drive". Contact me personally, if you want suggested sources for such adapters.

floppy drive controllers with conversion, imaging software

Some years ago, there were a series of floppy controllers for PC/Windows systems branded as the Compaticard product line. Some of them used internal floppy drives, some supported external floppy drives. Some of them could read Apple II and Mac diskettes. In any event, these products are long out of production and rare and are "ISA cards" only usable on VERY ancient PC-compatibles. So I don't "cover" the Compaticard here on this Web page. Same things apply to Central Point Option Board products. Search the Web.

SOme CP/M systems (and systems like the Apple II) used disk formats that conventional floppy disk controller boards can't read. There is/was a program and a bit of hardware called "Disk2FDI" which is described at this Web page. It uses a PC and a cable between a 5.25-inch floppy drive and the parallel port, and is said to be able to read Apple II and Commodore diskettes. A trial version is free to read only; there is a registration fee to get the registered version, from Europe.

Since about 2008, there's been a number of hobby-class projects to use programmable logic devices or embedded microprocessors as programmable floppy controllers. See my notes below.

Catweasel floppy controller

One company which offers at times (since 2000 at least) a floppy controller of sorts for the PCI bus is Jens Schönfeld of Individual Computers. who produces at various times the "Catweasel" series of PCI-board floppy controller. The controller does NOT include a 50-pin connector for 8-inch drives, but people have added such adapters. This is not a "standard" floppy controller and drives it uses are not available under ordinary MS-DOS, Windows, or Linux "file systems". No "A:> or B:> prompts, no "mount/unmount filesystems". The product is produced in Germany and sold by them or by resellers in other countries.

This product was primarily intended to support Amiga systems by providing a floppy controller and Amiga-type hardware to support Amiga emulation on Windows-type PC's. Other people have written software to operate it under MS-DOS or Linux, to read other disks and disk formats. Software development for it is scattered among a number of sites and people; the software runs under MS-DOS, Windows or Linux. I frankly suggest 1) reading the Web site (which is disorganized) and 2) conduct a Web search, to see who is doing what "currently", and where (and if) the current Catweasel board is available.

Many people were or are using these controllers for 8-inch floppy drives, or to read and write 5.25-inch and 3.5-inch Mac and Apple disks, or TRS-80 disks. And if you can program, this may be an option for running 8-inch drives with wierd formats on a Windows PC. The older Catweasel products were ISA 8-bit cards; some may still be available on the used market. Since late 2004, these models are PCI cards.

for some more Catweasel discussion, check my Web page on using it for very old Intel diskettes.

One software source for TRS-80 and other uses is Tim Mann's TRS-80 pages on the Catweasel. A Web search will find discussion group posts about specific uses and modifications of this software, or sites with more info and software for use. Go to my S-100 pointers page for possible links to other Catweasel sites or software developers. There's several other people who have developed software for use with this card; others over time have added to or adapted their work. There has been a Catweasel discussion group on Yahoo but it's not terribly active.

In Dec 2010, considerable work was done to read old ancient Intel 8-inch M2MF format diskettes which I chronicle on this Web page.

Software to read/write foreign diskettes on 1990's PC's under MS-DOS

IBM-PC compatibles of the 1990's and into the 2000's, provided a 5.25" or 3.5" floppy drive as 'standard'. The drive was operated by a "floppy disk controller" which was either a card (ISA, PCI) on the computer's "bus slots", or it was part of the motherboard's hardware. A number of software tools were developed in the period, to read and sometimes write non-MS-DOS diskette formats. Those tools ran under OS's like MS-DOS or Linux or Windows. I've collected information on some of these now-ancient products here. Look in the above section for add-on hardware for PC's to read foreign floppy diskettes.

Sydex's ANADISK and 22DISK; Teledisk

One software product to read old CP/M diskettes was developed and provided by Sydex Inc. and called "Anadisk" and "22disk". This product was produced in the 1980's to run under MS-DOS. It was offered in "freeware" trial form at no charge, as well as a licensed form for a fee. By the 21st century, the rights to the products were sold and it's no longer available. "Freeware" versions have been removed from many archive sites. But the originator of these products offers some degree of support to ORIGINAL licensees. Check this Web page for further history and discussion, including my correspondence with Chuck Guzis, president of Sydex and author of these programs.

"Teledisk" was another classic commercial product, to read and write "foreign" disk formats in the MS-DOS world. I don't have in hand the history of that product. But copies of Teledisk, and images collected in ".TDO" format, appear in many vintage computing archives.

Dave Dunfield's imagedisk

Check my "how to CP/M" Web page for more discussion of Dave Dunfield's MS-DOS-based imagedsk or imagedisk tools and his archive of system disk images. Dave's program, on a vintage MS-DOS computer with then-ordinary floppy controller and drives, transfers disk contents to and from an "image" file. Thus his program can recreate the original diskette. He also has software tools on his site to test PC's floppy controllers and drives to support single-density operation, which is not not supported on some vintage PC floppy controllers. This has become the primary tool for CP/M and other 8-bit system disk imaging and archiving. Dave's site has many "boot disk" images, plus means to support 8-bit systems with MS-DOS PC-incompatible floppy controllers.

Linux "raw" diskette utilities

My ignorance of Linux is vast but I'm not clueless. Linux has some raw "file system" tools at the command line level (they call it "the shell" or "the console") called simply "dd". There's also some vintage tools from Unix days for CP/M diskettes, called "cpmtools". Tools like "dosbox" will emulate MS-DOS to run MS-DOS-based software. There's similar emulators for CP/M-based software. Linux will also run some "Catweasel" hardware and software, discussed elsewhere on this page.

A more knowledgable colleage of mine, discusses dd, cpmtools, and working with Dunfield's IMG Imagedisk images, on a web page on his Web site. Mike Loewen shows how to read off old IMSAI CP/M disks with a mix of Imagedisk and Unix/Linux tools. Note that hardware-operating tools like Imagedisk, Catweasel, etc. must run "native" and not under emulation.

Omniflop and Omnidisk, software to read non-PC diskettes

Omniflop is a freeware product to read foreign diskettes on Windows-based PC's. Check the Web link for details. They have an older product, Omnidisk which runs under MS-DOS. These products read whole contents of a diskette, they apparently don't interpret the image into a file system (CP/M, FAT13, etc.). The site refers to other programs which do.

ubee512, software to read Microbee diskettes

Stewart Kay is the author of a Microbee emulator for Windows and Linux called ubee512. See my [link to be added] Web page of S-100 Web pointer for specifics. Additional to Stewart's emulator is a Windows/Linux software package to read, write and file-image floppy disks called "ubeedisk". Source, Windows image and Linux image files are available from the uBeeDisk repository at freshmeat.

Stewart described some attributes of Microbee disk formats and his ubeedisk program to me as follows: "My main interest is to archive Microbee disks which use 10 x 512 byte sectors. Often side one of the disk has the sector headers coded as side 0, also some other strange sector numbering can be used. The Microbee used non-standard GAP values, and fiddled the sync bytes in their native format programs, like some other Microcomputers at the time. So I need software that can cope with this and ImageDisk is able to do that. It also offers other useful diagnostics." He discussed some of its scripting capabilities which support ease of use, and suggests these features and Windows/Linux support provide an alternative to Dunfield's imagedsk.

Also needed for the Windows version, but not supplied with it, is a fdrawcmd.sys driver to access the floppy controller hardware. fdrawcmd.sys can be found at the author's Web site by Simon Owen. (Other diskette utility programs which use this driver are linked from that site as well). Stewart noted his program was written around LibDisk tools and uses the LibDsk library. Consequently it "can produce RAW or CPCEMU DSK and EDSK images or whatever is provided in the LibDsk library. It can read other disk image formats too but not write [them]".

Microcontrollers to read or replace floppy media

In the 21st century, hobbyists and techs are building "adapters" around inexpensive microcontrollers (Arduino, PIC, Atmel, etc) to either operate floppy drives and/or to emulate floppy drives; they are connect to personal computers through USB, generally. There are too many of these efforts to track, and some don't stay around. But I can describe how you can find them.

Generally these individuals or groups are devoted to a single brand or brand product line of vintage computer, like "Heath H8" or "MITS/Pertec". Many have Web sites or email-based discussion group Web sites; some are individuals who are presenting these as their projects; some are selling them as products. Commonly they 1) archive disk images, generally in a "raw" format; 2) describe and construct hardware tools by which they obtain and use those images on original hardware; and/or 3) offer software tools to use the images in emulators. In a few case, for commercial products like sewing machines or industrial controllers, they only offer the "widget", a solid-state floppy drive replacement unique to specific sewing machines etc., for several hundred dollars.

In many cases, these support groups don't try to use or accomodate previously available general purpose tools like IMAGEDSK. In my discussions with such groups, they often can't imagine using "their" disk images or files any other way, execept to provide images for emulators of the original (and specific) computer of interest. Unlike the general-purpose methods I've described, there's often no means provided to "extract" files from these images under Windows/MS-DOS/Linux systems, except by operating their emulators. If the emulator won't install well or if you simply choose not to run it, the alternative is to decode their image formats and to "program" extraction tools yourself.



Herb Johnson
New Jersey, USA
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