Stocking up a TRS-80 Model 4 with software


I love my Model 4. With its single case form-factor, it looks just like a vintage computer should. However, ever since acquisition the machine has sat in its box softwareless and lonely. It was simply a case of finding the time to load it with programs. In particular, I wanted to stock it with FLOPPY DOCTOR, hence turning the machine into a 5.25 inch drive-testing beast as described in this article.

A rainy day gave me the opportunity to correct this sad state of affairs and give the Model 4 the software library it deserves.

Deciding on the best option for transfer

I had to get software from Internet-sourced disk images onto real disks. There are a number of ways I could have approached this task. These included RS-232 transfer, using the Semi virtual diskette (SVD), or using an emulator with the capability to write to real disks. I explored the SVD first but found while it seemed to work with most images it was a no-go with protected autoboot programs like FLOPPY DOCTOR. After some research I decided to use David Keil's TRS-80 Model III/IV emulator. This program allowed real disks (including many autoboot protected disks) to be made from disk images.

David Keil's emulator running TRSDOS 6.2

Figure 1. David Keil's emulator running TRSDOS for the Model 4
(image from

Setting up a MS-DOS platform

Using David Keil's emulator presented one problem. It could not make real disks using a Windows XP platform. It needed low-level access to the hardware hence MS-DOS was necessary. I'd faced the same problem in making Kaypro disks and had used my 386-DX40 machine for that task. This needed something faster though.

The solution was a MS-DOS 6.2 Pentium box I had tried (and failed) to sell for $1 on our local auction site. Although it's an ugly beast, I decided to make this my permanent legacy disk-burning machine for both the Model 4 and CP/M micros. I installed a spare 360k floppy drive I had lying around, and loaded the machine up with both the Keil emulator for the Model 4 and Dave Dunfield's CP/M disk-making software. A 3.5 inch drive was used to transfer the necessary disk images from my Internet-capable XP box.

Finding the software

The next step was to find the software. The Model 4 has an automatic Model III mode, so software for the latter platform was just as valid. Specifically I was looking for:

I had plenty of TRS-80 Model 1 software. Although many programs were compatible, there are enough differences between the Model I and Model III/IV for Model 1 programs to have issues. I needed specific Model III versions. Again it was David Keil to the rescue. David's website also contained downloads for most of the software I wanted. I had problems with some of the game images (see later) but this site provided the bulk of my new library.

Making the disks

I found the section on how to make real disks from images wasn't that easy to find amongst David's instructions. Finally I figured out that I had to use a special disk image that was bundled in with the support files. Writing to this disk image actually wrote to a real drive. Once I'd discovered this, I was up and away!

Copying was done with a program called Copycat, also from David's software library. This made a track-by-track image on the floppies. After producing each disk I'd check it for integrity, first in the emulator then in the real Model 4.

making TRS-80 Model IV disks.  It's ugly but it works!

Figure 2. Making real disk from disk images on the MS-DOS Pentium

While most of the transfers were smooth sailing I ran into a few problems. Firstly, some images were of double-sided disks, whereas my Model 4 disks were single sided. Second, many of the autobooting games disk images contained single-density tracks in order to recognise Model I systems. These failed to write correctly.

Thankfully delving down in my own archives, I found a large double-sided 80 track disk image labeled "Model 3 games". I must have downloaded these games sometime in the past for use with Matthew Reed's TRS32 Model I/III/IV emulator. What's more, I found it dead easy to extract these files, then re-constitute them into four single-sided, 40-track LDOS disk images using Matthew's wonderful TRSTOOLS program. This worked well and I soon had the games I wanted on real disks. TRSTOOLS was also useful for splitting up those other large double-sided disk images mentioned above.

In the end I had everything I wanted including the coveted FLOPPY DOCTOR.


The Model 4 now has a library of software on 5.25 inch floppies. This would not have been possible if it were not for the creative works of David Keil and Matthew Reed. I salute you both. Also, thanks should be made to the writers of all this old Model III/IV software which the vintage computer community can now enjoy from a historical perspective.

Software-enabled Model 4

Figure 3. TRS-80 Model 4. Locked, loaded and ready for action

I'm looking forward to exploring Montezuma Micro's CP/M and doing more work on my flaky Kaypro II B drive using FLOPPY DOCTOR. It was good checking out the arcade games again too. Even though I was very familiar with these from the Model I, the Model III versions often had extra features and screens.

Original article 27th December, 2010, Updated 22nd May, 2017

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