How to read and write old floppy disks

This Web page last updated dated nov 18 2012

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. This information was on that page until Sept 2011.

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

Windows or Linux floppy disk controllers & software

Some people ask: "I want to read 8-inch diskettes on my PC/Windows/Linux machine. Please sell me a complete system, or tell me where to get one." Often they have no idea how this might be accomplished. Other 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. Folks, this is not a "plug and play" project. A few people want to read really ODD formats - hard sectored, M2FM, and so on.

In the 21st century, you have two choices to accomplish the above goals. 1) Buy some special-purpose, privately produced, floppy drive interface for 3.5" or 5.25" floppy drives. Add an adapter to make 8-inch drive connections if you want that. Use the software offered with the interface. This only works with now-standard double density formats and some single density formats.

Or 2) get an older PC with a floppy controller (add that 8-inch connection thingy if needed), and use added software on the PC to "handle" the odd format under program control. Neither solution 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.)

To read 8-inch floppy drives on a "PC", you can in principle connect 8-inch drives to a PC'/s floppy controller; you "just" need a drive, with power supply; a 50-pin cable; a connector to adapt 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 on Dave Dunfield's IMAGEDISK for details.

Reading non-MS-DOS disks on a PC, even with the right sized floppy drive, 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. 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.

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

As for 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 an adapter, consider D Bit's 8-inch floppy disk adapter for 8-inch drives on PC\windows systems. While they don't provide PC software for CP/M diskettes, they do have an MS-DOS utility for PDP-11 diskettes called "PUTR" that may be relevant. While this adapter was still listed at dbit.com as of 2007, their supply and services may vary.

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. So I don't "cover" the Compaticard here on this Web page. Other Web sites cover that product line, a Web search may find them.

Also some years ago, there were the Central Point Option Board products. These were ISA bus boards (for old IBM-PC compatibles well before the Pentium) which provided ways to copy either Apple or Mac diskettes, or old "copy protected" diskettes. I found a reference in a comp.sys.tandy Usenet group discussion in 2010 to this Web page about the Central Point products, including manuals photos and software. Again, search the Web for information on this old product line.

Since 2000 or so, there's been a series of bus card products (ISA bus, PCI bus) built for use with PC's called Catweasel, by German company Individual Computers. Follow this link for more Catweasel information.

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. Search the Web for these as they come and go. In 2010/11, one project is Kryoflux, an ARM processor programmed to read floppy data streams. They are associated with The Software Preservation Society (SPS), formerly the Classic Amiga Preservation Society (CAPS).

ANother microcontroller floppy controller is Device Side Data's FC5025 USB 5.25" floppy controller. This is a read-only USB device. Software drivers Linux, Mac OS X and Windowsare provided with source, to read a variety of formats including Apple and Commodore, apparently as diskette image files. The device reads flux changes, not just FM/MFM "standard" bit encoding. Some specific disk formats are supported (to extract files). It's unclear if hard sectored disks are supported but others (SEBHC Heath group) are discussing this topic. Price appears to be under $59 US. The vendor appears to be a private individual or group of some sort, working on imaging Apple diskettes since 2007.

A search of various "vintage computer" discussion groups, including those dedicated to specific 8-bit systems, will likely show other disk reading projects in progress. The primary effort seems to be to "archive" disk images, for running in emulators or to reproduce as running disks.

Catweasel floppy controller

One company which offers a floppy controller of sorts for the PCI bus is Jens Schönfeld of Individual Computers, who produces the "Catweasel IV" controller. The controller does NOT include a 50-pin connector for 8-inch drives, but people have added such adapters.

The Catweasel IV floppy controller product is produced in Germany by Jens Schönfeld of Individual Computers. It is sold by some US and European companies. 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. I regret to say it's hard to find current information about the Catweasel on the Individual Computer Web site, And, software development for it is scattered among a number of sites and people and operating systems. I frankly suggest a Google search, to see who is doing what "currently". I'll try to provide some directions on this Web page.

Many people 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, the Mark IV model is on a PCI card. (In 2010, they have a new PCI model. This site seems to be a catweasel distributor.)

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

The Individual Computers site lists distributors for the CatWeasel Mark IV, or you can buy direct from Germany, or in 2010 there were some new cards offered on eBay. One support 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 of this product, 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 apparently several people who have developed software for use with this card; others add to or adapt their work over time.

In 2009 I was alerted to Karsten Scheibler's site; there is software there plus links to other developers. There's also a Catweasel discussion group on Yahoo but it's not terribly active. Again, a Google search may be more productive.

In Sept 2010, I was contacted by Larry Kraemer who did some Catweasel work on TRS-80 diskettes. His TRS-80 Model III & IV posting is on the Ubuntu Forum (Linux) at this link as of that date.

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

In Dec 2011, courtesy of the Catweasel Yahoo group, I saw mention of an open-source Catweasel code release called Arunja from 2004. It's hosted on the card manufacturer's Web site. One person appears to be responsible for this code. Check the site for details, note software requirements for use.

In NOv 2012, a colleage alerted me to Catweasel work done on Northstar (Horizon, Advantage) hard-sectored 5.25-inch diskettes by Andrew Lynch. His programs and I presume some discussion are/were in the Northstar computer Yahoo discussion group files. YOu have to join the Yahoo group to access them.

Software to read/write foreign diskettes on modern PC's

A number of software tools were or are developed to read and sometimes write non-MS-DOS diskette formats on MS-DOS or Linux or Windows systems, using their on-board floppy controllers. I'll collect information on these products here. Look in the above section for add-on hardware for PC's to read foreign floppy diskettes.

Sydex's ANADISK and 22DISK

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.

Dave Dunfield's imagedisk

Check my "how to CP/M" Web page for more discussion of Dave Dunfield's MS-DOS-based imagedisk tools and his archive of system disk images. Dave's program transfers disk contents to an "image" file which can be used with his program to 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. 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.

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]".



Herb Johnson
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