Converting TRS-80 Disks for use in an Emulator

The Problem:

Modern hardware and operating systems are making it more difficult to convert actual TRS-80 disks into an emulator (DMK or DSK) format.

Some of the obstacles are:

  • No ability to read single density disks whatsoever
  • Current operating systems do not allow for direct hardware addressing
  • No 5.25″ drive support in the BIOS
  • Degrading media (See Warning below)

Different Methods:

There are a number of different methods you can try, all of which are covered on this page:

  • Send them to me
  • Ancient PC
  • Modern Day Solutions

Send them to me:

Disks which are 35+ year old may have no more than 1 good read on them. If the disks were exposed to any level of humidity over the past 35+ years, odds are that the mylar will separate on the first read. While I cannot guarantee results, I can guarantee that if you try to read them first, I won’t be able to. Please see this FAQ.

Ancient PC:

Reading single-density disks (which is what the Model I used; noting that even double density disks tended to have a single density track 0) is MUCH more complicated. “Modern” computers do not have the crystal needed to generate a single density clock, so they simply cannot read single density. Even those that can will have trouble with TRSDOS 2.x (DAM problem) or NEWDOS/80 v1.x (DAM problem) or NEWDOS/80 v2.0 (Inner Track Problem).

To convert Model I disks (other than TRSDOS or NEWDOS/80) to emulator format you will need:

  • A 5.25″ disk drive (obviously); and either
    • A very very very old PC (i.e., IBM PC/AT, PC/XT, or the like) to get BIOS Support
    • A PC with an ISA port and any of the following:
      • The Adaptec 1522 SCSI controller (ISA, non-bus-mastering, NS8473 Controller) can read/write/format FM (Single Density) floppies, including LDOS-format SD floppies. TRSDOS2.3 directory tracks CANNOT be handled on these because of the DAM.
      • It is possible that the Adaptec 1542 SCSI controller (ISA, bus-mastering, NS8473 Controller)
      • The Acculogic ISApport SCSI adapters (SMC FDC37C65) will read 360K Double Density but will not read single density on a 1.2MB HD drive.

To convert Model I TRSDOS or NEWDOS/80 disks to emulator format you will need:

  • A 5.25″ disk drive (obviously); and either
    • A working TRS-80 Model I (where you would then copy the files to a more friendly OS like LDOS)
    • A working TRS-80 Model III or 4 (where you would then copy the files to a double density operating system)


Before putting a disk in your drive, make sure to inspect it. Improperly stored disks will degrade, and will shred in your drive. Inserting one of these disks in your drive will not only produce a disheartening noise, but will likely coat your read/write head with oxide, requiring you to clean the heads. Here are some pictures I took of some of these improperly stored or otherwise decayed disks.

Reading/Writing TRS-80 Disk Media on a PC

If you have a 5.25″ drive hooked up to your IBM PC, the following programs can be used to read TRS-80 disks into the DMK/DSK format. If you want to read Model 1/3/4 disks and have a Catweasel card, use Tim Mann’s CW2DMK utility. If you want to read Model 1/3/4 disks and do not have a Catweasel card, use Matt Read’s READDISK utility. If you want to read COCO disks, use Jeff Vavasour’s RETRIEVE utility.

Utility Name
Last Updated
Home Page

Utilizes special hardware called a Catweasel card to read all formats of TRS-80 disks on a PC. Also includes a utility of general use for converting DMK format disks to DSK format.

May 19 2014
George Phillips based on Tim Mann’s v4.4

Unofficial build with takes Tim Mann’s v4.4 and adds additional features: [1] Ability to cache good sectors and output the best possible read, [2] Ability to continue retrying once the retry count has expired, [3] Senses MS-DOS Format on Side 2 and ignores it, [4] Ability to drump raw track data into files.

READDISK transfers files from a TRS-80 Diskette to an IBM .DSK file without special equipment. This version can also read Tandy 1000 disks.

Please note that not all PC disk controllers are capable of reading TRS-80 disks. This is a limitation of the disk controller, not READDISK. If you have trouble, try running READDISK on other PC’s until you find one that can read your disks. Remember, you only need to read your TRS-80 disks once to convert them to disk images, so be sure to use the “Retry” command heavily.

Modern Day Solutions:

There are a number of third party products which can be used, to varying degrees of success, to read TRS-80 disks.

These include:

However, Flux Readers put all their weight on the software. If the software running them is not performing CRC error checking on the sectors and verifying the sector count per track, then you really get what you get, and on 40+ year old disks, that is likely to be a bad read. The flux reader will read a bad sector and store a bad sector, but it will never try to re-read that sector to get a good read, so you are locked into a bad sector, which is really not ideal.

Also, conversion from the proprietary flux reader software to a DSK or DMK image usable in an emulator is also likely to produce substandard results in that copy protection and anything other than a standard format is likely to be misinterpreted by that conversion software..

Reading/Writing TRS-80 Disk Media on a PC – MUCH older utilities

The following programs are over a decade old and regardless of whether or not they even work, the above are much better choices at this point in time.

Utility Name
Last Updated
Home Page

To transfer files from a COCO Diskette to a .DSK image.

Jan 5, 1999
Timothy Purves

Transfer runs on a TRS-80 and will read/write to IBM PC Formatted 5.25″ disks.

The TRS-80 Model 4 Emulator’s virtual disk utilities have been provided free for download in order to allow you to determine whether your PC has the features necessary to read and write TRS-80 floppies directly. The emulator can either access your TRS-80 floppies directly in its floppy drive, or as images copied to your hard drive. Either way, you need to be able to determine whether the PC hardware can read the floppies.

Reading, writing, editing and formatting TRS-80 disks on a PC.

Mar 20, 1990


  1. I recently used spark plug cleaner to clean disks in bad condition and was able to read data from them after a little spray straight on to the platter ! as a last resort I was amazed it worked 🙂

  2. I have a couple of 5 1/4 floppy disks that have our Christmas letters from 1982 & 1983 on them. I would like to get this data recovered. Any idea where I can go to get this done?

  3. I have a TRS-80 Color Computer 3 and an original color computer disk drive, and I got my cassette programs onto disk on my own. However, I have no clue how to get my programs from the floppy disks into a virtual format that I could preserve on modern equipment, and I really wish I could do that. I do have a late 1980s/early 90s DOS/Windows 3.1 PC with a 5 1/4 floppy and a 3.5 floppy, and a late 1990s PC with a 3.5 floppy and a CD-R/W, and a couple of newer machines. But the PC could not read the TRS-80 disks, which I imagine is a problem of format but I am not up on these things. My programs are all basic and I saved them in ASCII format, but I’m guessing the problem is deeper than that. If you have the know-how and the equipment, I’d be happy to pay for a conversion of my disk (I have one disk to convert, at most I may have a second one but as of now I just have one). Thoughts?

  4. Hello I have hundreds of 5 1/4 Double Density floppies formatted for MS DOS. I would like to have these converted to a contemporary media, is it possible? It’s for an archive project for a writer.
    Thank you


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