Tag Archives: TRS-80

The TRS-80 Microcomputer RFI Testing Report

By | June 6, 2020

Soon after the release of the TRS-80 Microcomputer in 1977, it became apparent that the computer was emitting significant amounts of RFI (Radio Frequency Interference). A common story at the time is that you could generate primitive sound effects for games by simply placing an AM radio next to the computer. This was a hot topic at the time for many of the new microcomputer manufacturers, including Radio Shack’s competitors TI and Apple, because the FCC soon became involved. Complaints poured in from amateur radio operators and television viewers who were being negatively affected by their neighbor’s new computers. read more

TRS-80 8 MB Hard Drive Three Wire Fix

By | September 15, 2018

Starting in 1981, Tandy Radio Shack released a number of different hard drives for their popular line of microcomputers. The first one to be released was the 8 MB Hard Disk Drive for the TRS-80 Model II. This unit contained an 8″ Shugart SA1000 hard drive bubble along with an 8×300 based controller board. With the subsequent industry introduction of the smaller 5 1/4″ MFM hard drive bubbles, the next hard drive unit released was the much smaller 5 MB Hard Disk for the TRS-80 Model I and III and a similar 12 MB Hard Disk for the TRS-80 Model II and 16. Future updates included the 15 MB, 35 MB and 70 MB units which were all sold for the Model II/12/16/16B/6000 line of business computers.

All of these hard drive units were built by Radio Shack and consisted of several components: the hard drive bubble, the controller circuit board, power supply, cooling fan, keyed power switch, activity lamp, write protect switch and wiring. The power switch, activity light and write protect switches required special wiring that tapped into certain signals on the hard drive bubble to function properly.

This wiring becomes an issue when you want to replace the hard drive bubble with one that is different from those that were provided by Tandy. The common solution typically applied was written about by Roy T. Beck in a series of articles called “My Adventures with Hard Drives”. Ian Mavric elaborated about this fix in the June 2013 issue of TRS8BIT. Roy’s fix involves moving the three wires from the bubble to matching locations on the controller board. Once this fix is applied, you can easily swap in different MFM hard drive bubbles with ease.

While Roy’s article mentions the 8 MB Hard Disk as the original implementation of the Tandy 3 wire configuration, the fix he defines only applies to the later 5 1/4″ hard drive units. Since I am an enthusiast of the Model II line of computers, I’ve spent some time figuring out the appropriate fix for the earlier 8 MB hard drive unit. The fix is listed in the table below which I suggest to be added as an addendum to Roy’s article.

While the wires in the 8 MB unit tap the same signals as those referenced in Roy’s article, the wires are different in color.


Addendum to Table 1

Master 8 MB Hard Drive with 8X300 Controller (Note 7 & 8)

Wire Color Function Original SA1000 Connection Generic Connection
Orange Drive Select E2 Pin 1 HDC J6 Pin 26
Blue Write Protect J2 Pin 5 HDC J1 Pin 5
Brown Seek Complete C3 Pin 8 HDC J6 Pin 8


7. All of these wires should be soldered to the underside of the HD controller board.
8. This configuration is only for the primary 8 MB Hard Drive.


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TRS-80 BASIC Image Generator

By | September 9, 2018

This tool will allow you to convert any image accessible via a URL into a BASIC program that can be run on the TRS-80 Model I and III microcomputers. The generated BASIC program should run on any TRS-80 BASIC on the Model I and III, including most if not all emulators, as well as on the Model 4 when running in Model III mode. The images will be displayed in the standard TRS-80 128×48 monochrome resolution.

Go to the BASIC Image Generator Tool

Here are a few examples of images generated by the tool

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Breakdown – A New TRS-80 Game

By | March 4, 2018

Breakdown is a game for the TRS-80 Microcomputer. It should run on any TRS-80 Model I, III or 4 with 16K or more of RAM. Breakdown is inspired by the classic video game Breakout and to a lesser degree Tetris. The goal of the game is to score as many points as possible by breaking as many bricks as possible with a bouncing ball while trying to keep the ball in play and avoiding falling bricks.

The game is a work in progress. There are currently 8 different levels in the game.  If you complete all the levels then the game ends.  My thought is that there will be many more different levels added to the game.  Each level takes 80 bytes to define, so we could realistically easily have 100 levels on a 48K system.

Breakdown is freeware and you are free to use it for personal use.

Download the full package including instructions here

Download Breakdown

or stream Breakdown from your mobile phone to your TRS-80 using the cassette port here

Breakdown Cassette WAV (Low Speed 500 baud)

  1. Connect mobile device to the TRS-80 cassette port
  2. Type “SYSTEM”
  3. At *? prompt type “BREAKD”
  4. Click WAV link above to start playing WAV audio
  5. At *? prompt type “/”

Breakdown is written in Z-80 assembly. It was developed using George Phillip’s zmac cross assembler.

Breakdown in action

I originally wanted to release Breakdown as a real packaged software product, with a paper manual and pre-recorded cassette tape. This was how many TRS-80 games were sold back in the day. However, at this time, I am just too busy to go through the effort of creating the manual and tapes at the level of quality that I would require. Maybe I will do this for a future game.

Let me know how the game works for you and what features you would like to see added. read more


By | November 26, 2016

TRS-Pic is a Google Images browser for your MISE equipped TRS-80 Model I or your M3SE equipped TRS-80 Model III or Model 4 with a broadband internet connection.


Watch the video

You can download TRS-Pic here trs-pic-0.1.zip.

Once you unzip, you can copy the appropriate commands for your TRS-80 using the MISE/M3SE FTPD service. Be sure to transfer using Binary mode. See the README.TXT for more details.




You can search for images just like you do in Google Images. Here is what the TRS-Pic title screen looks like on a TRS-80 Model I.







Here is Boba Fett as viewed on a TRS-80 Model 4 with a Hi-Res card.





The search results screen on a TRS-80 Model 4.








Here is Boba Fett again, this time viewed on a TRS-80 Model I with standard 128×48 resolution.






Here is Boba Fett again, this time viewed on a TRS-80 Model I using the MISE PCG-80 emulation on a VGA monitor.



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TRS-80 Model II Archive Project

By | September 14, 2016

Note: When we refer to the Model II we mean the entire Model II line of computers that includes the Model II/12/16/16B/6000.

Do you have any TRS-80 Model II 8 inch floppy disks laying around? Maybe you no longer have a Model II but you held onto your disks or maybe you obtained the disks by themselves. If so, you can do your part to help the vintage computing Model II community by sending in your floppy disks for archiving into the Model II Archive.




Do you have a Model II but your computer’s 8 inch disk drive is not working? You can send in your disks so that they can be imaged for you and we will provide you with digital copies. You can then use these digital floppy images in a modern floppy drive emulator like the HxC on your Model II.


Maybe you have a Model II computer with a working 8” floppy drive but you have no disks to test or to use the machine? We can send you some working physical DOS disks upon request. Understand that 8” media is becoming rarer by the day so please limit your request to a few different DOSes. We can provide disks of most DOSes found in the Model II Archive.

Do you have Model II manuals or documentation that you no longer need or plan to throw away? Please consider sending them in to be scanned and placed into the archive for the use of current and future Model II enthusiasts. Or scan them yourself and send us the PDFs if you have the time and inclination to create quality scans.

Contact Us to find out more or to send in your artifacts.

There are a few reasons we’re offering this service.

First, is to foster the restoration of these beautiful computers and to build a strong community of TRS-80 Model II enthusiasts. If you have digital floppy images you will be much more likely to want to use your Model II since you are eliminating one of the major problems with these computers today…finding and maintaining working 8” drives and media. Most of these machines led a hard life in business environments and are typically non-functional, especially the floppy drives. So it is especially rewarding to get one of these computers up and running. Using digital media makes that task much easier.

Secondly, you may have software or documentation that is no longer available anywhere else. It is quite possible that you could have the only working copy of some original Model II software. There are Model II manuals that I have never seen that may or may not still exist. By imaging your disks and documentation, you can help to build the collection of rare artifacts in the Model II Archive. This archive is concerned exclusively with the preservation of artifacts for the TRS-80 Model II so that future enthusiasts can keep these historically important microcomputers operational.

Not all software submitted will be put into the archive. We endeavor to maintain only clean master copies of software. This is not always possible so there may be multiple copies of various quality of a particular title. Also, there may be some titles that the known copyright owner have asked us to not include in the archive. We always respect these legitimate requests. But those requests are few because the need for preservation of these rare artifacts is understood and supported.

Please note that we will filter out any personal information before placing images into the archive. If you send us your disks we will generally not return them to you unless you ask. The reason is that we will reformat and reuse any good 8″ disks after imaging them to create working DOS disks for other enthusiasts. We’re a community of collectors helping each other out…give and take. If you definitely require to get your disks back, we would request that you send the return shipping costs and try to just make it easy for us to send them back by sending them in a reusable shipping container.

This service is inspired by and adheres to the concepts laid out by Ira at trs-80.com. Ira has offered these types of disk services for many years for the TRS-80 Model I/III/4 machines. He has expressed his support for our efforts to do likewise for the Model II line of computers.

Any questions? Please read Ira’s FAQ which pretty much applies to the Model II 8” services as well. Please make sure you read through it before you consider sending your disks.

Before requesting DOS disks, please make sure your Model II can start up properly and boots to the “INSERT DISKETTE” screen. Please don’t bother requesting disks until you can get to this point. When you request DOS disks we will ask you some questions to ensure your system is in working order.

Please also consider sending a donation. Maintaining the aging imaging equipment and obtaining good working 8” floppy disks is not cheap. Especially given the age of the 8” media, and the issues that old media can cause with floppy drives.

You can get technical help with your Model II from the strong community of enthusiasts at the VCF Tandy Forum. read more

TRS-Box Serial

By | July 31, 2016

TRS-Box Serial Beta

You can now use TRS-Box without the need for a MISE or M3SE. All you need is a serial-IP adapter and a RS-232 interface in your floppy or hard disk enabled TRS-80. Many TRS-80s already have an RS-232 interface installed. You can find them on eBay or from TRS-80 specialists if you need to purchase one. Ask here if you need help finding one.

TRS-Box Serial has been successfully tested on the following platforms:

  • TRS-80 Model 4D 64K with LDOS 5.3.1 and LS-DOS 6.3.1
  • TRS-80 Model III 48K with LDOS 5.3.1
  • TRS-80 Model I Level 2 48K with LDOS 5.1.3 and LDOS 5.3.1
  • TRS-80 Model II/16 with LS-DOS 6.3.1

I am able to achieve consistent and reliable 19.2K baud transmissions on the Model I/III/4 and 9600 baud on the Model II/16 using the ATC-1000 serial-IP converter. At this time, I can’t guarantee it will work on other DOSes or models of TRS-80, but it may. I will be testing on more platforms soon. If you have a particular request or success story with another TRS-80/DOS combination, please let me know.

Remember, this is beta software, so please expect problems.

TRS-Box is free to use during the beta period for the express purpose of copying files to and from your TRS-80. Any other use or abuse of the system will result in blockage or removal of access to the service.
ie. Please don’t ruin it for everyone else. 🙂

TRS-Box Serial Setup

The ATC-1000 TCP/IP to RS-232 converter.

  1. Purchase a serial-IP converter. I highly recommend the ATC-1000 as it is reasonably priced, performs well and I have tested TRS-Box with it extensively. You can also try to use serial-IP proxy software running on a modern PC, however I have not tested this scenario. I prefer to use a standalone adapter as it is really an accessory rather than a whole modern computer and helps to keep the retro feel.
  2. Hook up the serial-IP converter as per its instructions. Important: You need to connect to your RS-232 port with a null modem cable. You also connect the converter to a broadband connected router on your network using an Ethernet cable.
  3. Configure the serial-IP adapter TCP/IP settings to connect to the TRS-Box services:
    Server/Client: Client
    Port: 21
  4. Configure the serial-IP adapter UART settings as follows:
    Mode: RS-232
    Baudrate: 300*
    Character bits: 8
    Parity Type: Even
    Stop Bit: 1
    Hardware Flow Control: None
    Delimiter: CR(13) and LF(10)
    *Make sure the baud rate you specify here is equal to the baud rate you set up using DB SETUP BAUD.
  5. Get the TRS-Box v0.7 beta software here. Copy the correct DB/CMD program for your model of TRS-80 and DOS to your TRS-80. See the README.TXT in the distribution. This may be the most challenging prospect for novice users. There are a myriad of ways to accomplish this task, such as using a PC-Serial transfer program like XMODEM, FreHD, MISE, etc. The good news is that once you have TRS-Box working, you won’t need to perform this task again! As a last resort, we can send you a floppy disk pre-loaded with the program for a small fee.
  6. Test your serial port connection using the following command DB TEST. If you get a success message, then proceed to step 7. If not, then you need to troubleshoot the connection. Here are some things to look for:
    • The problem may be in your settings from step 3 or 4. Make sure they are correct.
    • Check your cables. Are you sure you are using a null modem cable or adapter? You may want to obtain an RS-232 tester.
    • Your internet connection may be blocked. Make sure your router allows port 21 traffic out from the serial-IP adapter.
    • It not uncommon for the UART on the RS-232 interface to go bad, so you may have a hardware problem.
  7. Log into TRS-Box on your PC or Mac here using your Dropbox credentials. You will notice that you sign into Dropbox on the secure Dropbox website. TRS-Box never sees your Dropbox username or password. TRS-Box will also only have access to a special folder in your Dropbox called “Apps/TRS-Box”. This is where you will put your TRS-80 files.
  8. Once you obtain the TRS-Box token, type DB SETUP TOKEN YOURTOKEN.e.g. DB SETUP TOKEN 1234567890 If you see a success message then you are ready to use TRS-Box! Keep in mind that the token will expire from time to time so you may need to re-login occasionally.
  9. Type DB ? to see the various commands and options.
  10. Have fun managing your TRS-80 files!


Start at 300 baud to make sure everything is working ok. Keep in mind that large files will take a long time to transfer using 300 baud. For 300 baud, every indicator “.” (period) that shows up during the transfer process represents 64 bytes.
To find your maximum reliable transfer speed, ramp up the baud rate in succession from 300 to 1200 to 2400, etc. and test your transfers at each step. Once you get to a speed that no longer transfers reliably, then back down to the previous speed. This should be considered the maximum transfer speed for your particular setup. The maximum speed is affected by many factors, including the speed of the CPU and the capabilities of your serial-IP adapter.

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By | January 2, 2016

TRS-Box now works with TRS-IO!

You can now use TRS-Box with the trsnic TCP/IP stack in the TRS-IO card on the Model III and Model 4.  Get v0.8 of the TRS-Box client to start using your TRS-IO card!

TRS-Box now runs on the Model II and 16!

Finally, a modern file management solution for the big 8″ Tandys! You can now use TRS-Box Serial on your Model II/12/16/16B/6000 microcomputers. You’ll need to be running LS-DOS 6.3.1. Check out TRS-Box Serial for more information.

TRS-Box now supports Encryption!

Use the new ENCRYPTION setting with DB SETUP to turn on encrypted transfers. TRS-Box will run much slower when encryption is turned on, but your transfers will be confidential. Now, this is not SHA-256 with RSA we’re talking about here! We’re using a 128bit lightweight encryption algorithm. That’s about the best we can do on a Z80 8bit machine and still have a useable experience. So, while your transfers are fairly confidential, you should still not transfer any data of significant value, like banking credentials. Then again, why would you do that with your TRS-80?

What is TRS-Box?

TRS-Box is a Dropbox client for the TRS-80 Microcomputer. It allows you to navigate and copy files from and to your Dropbox from your TRS-80. It is an easy and powerful way to manage the files on your TRS-80.

TRS-Box requires a TRS-80 Model I with MISE or a TRS-80 Model III or 4 with M3SE or TRS-IO setup with a broadband Internet connection and a Dropbox account.

If you don’t have a MISE, M3SE or TRS-IO, then check out TRS-Box Serial.

To use TRS-Box you will first log into your Dropbox account and give permission for TRS-Box to access it’s folder in your Dropbox.  Authentication takes place on the secure Dropbox site so TRS-Box never has access to your Dropbox credentials.  TRS-Box will only have access to its own folder found at Apps/TRS-Box.  This is where you will place your TRS-80 files.

Get started here and follow the directions.

The TRS-Box Commands

You can download the TRS-Box commands here trs-box-0.8.zip. Once you unzip them, you can copy the command programs to your TRS-80 using the MISE/M3SE FTPD service. Be sure to transfer using Binary mode.

Viewing the contents of a Dropbox folder on a TRS-80 using the TRS-Box db dir command.

  • db setup – Configures TRS-Box.
    e.g. db setup token 1111111111
  • db pwd – Shows the current working folder in Dropbox
  • db cd – Changes the current working Dropbox folder. You specify the folder to switch as a parameter. Standard directory techniques apply such as “..” to move up a folder. Use quotes when folders have a space.
    e.g. db cd "Another Folder"
  • db dir – Shows the contents of the current working folder in Dropbox
  • db get – Retrieves a file from Dropbox. You specify the file name of a file in the current Dropbox folder and a TRS-80 filespec for where you want the file to be copied.
    e.g. db get readme.txt readme/txt:2
  • db put – Copies a local TRS-80 file to Dropbox. You specify the TRS-80 filespec of a file on the TRS-80 and a filename for where you want the file to be copied in the current Dropbox folder.
    e.g. db put readme/txt:2 readme.txt


  • This is beta software and is more than likely to occasionally crash and freeze your TRS-80 from time to time. Don’t worry…a simple system reset will get you going again.
  • If you run into problems, try getting a new token and running dbsetup again. Let me know if you continue to have issues.
  • During beta, please don’t copy over important files without suitable backups in place.

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TRS-80 Model III Computer Graphics Image Generator

By | August 7, 2015

This tool will allow you to convert any image accessible via a URL into a format compatible with the TRS-80 Model III with the Computer Graphics high resolution upgrade option. This format is also used in the Model II Computer Graphics and the Model 4 Computer Graphics packages so these generated images will work on all 3 of these TRS-80 platforms.

Go to the Image Generator Tool

To display the images on your TRS-80, use the GLOAD program provided with the Computer Graphics software. The program listing of GLOAD in the Computer Graphics documentation is hopelessly broken so I rewrote it here GLOAD/ASM for those that are interested. It functions identically to the original GLOAD binary.

Here are a few examples of images generated by the tool

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By | April 13, 2015

TRSWiki now runs on the Model 4 with LS-DOS 6!

The Model 4 running LS-DOS 6 provides a 80×24 character screen size which makes Wikipedia browsing even more enjoyable.

The TRSWiki splash screen on a Model 4 with the M3SE and Hi-Res graphics card

80 column Wikipedia entry for Star Wars as rendered by TRSWiki on a Model 4 with the M3SE running LS-DOS 6

Portrait of the Lost in Space family as rendered by TRSWiki on a Model 4 with the M3SE and Hi-Res graphics card.

See TRSWiki in action

TRSWiki is a Wikipedia client for the TRS-80 Model I, Model III and Model 4 computers. TRSWiki currently requires the MISE – Model I System Expander or M3SE configured with an Internet connection.

Example of image of Darth Vader as rendered by TRSWiki using PCG-80 Hi-Res mode on a Model I with the MISE

The search results page for “TRS-80” as rendered by TRSWiki

Portrait from the Abraham Lincoln Wikipedia page as rendered by TRSWiki using PCG-80 Hi-Res mode on a Model I with the MISE


  • is beta software that will more likely than not crash from time to time. Let me know if it is not working for you.
  • supports Wikipedia searches, text-based content browsing with functioning hyperlinks and image viewing.
  • requires that you setup your MISE network configuration to access your broadband Internet connection. Note: You need to run the DHCP application included with MISE before running TRSWiki.
  • has been tested on a Model I with MISE, Expansion Interface and 48K as well as a Model III with M3SE and 48K. It may work with other supported MISE configurations. If it does, please let me know.
  • supports PCG-80 Hi-Res graphics mode. Unless you have an actual PCG-80 modification to your Model I, you’ll need a VGA monitor connected to your MISE in order to view the hi-res images using the MISE’s built-in PCG-80 emulation. Use trswikih.cmd for hi-res support.
  • utilizes an intermediate proxy server to perform the heavy lifting of processing wiki content into a format useable by the Model I.

Download TRSWiki v0.9

Once you have extracted the appropriate WIKI/CMD from the zip file to your modern computer you can copy it to your TRS-80 using the MISE FTPD service. Remember to use binary transfer mode.

Example of image from the Star Trek Wikipedia page as rendered by TRSWiki

Example of image of Han Solo as rendered by TRSWiki

The Star Wars Wikipedia page as rendered by TRSWiki

Known Issues

  • Lowercase is supported on Model I computers with the lowercase hardware modification. If you do not have a lowercase mod, make sure you run the MISE UPCASE utility.
  • I’m not too happy about how I am currently representing hyperlinks, ie. <-#-> following or leading the anchor text. But, I have yet to think of a better way given the Model I limitations. Let me know if you have a better idea. Also, the maximum number of links supported on a screen is 36 due to the available number of keyboard keys. On pages with more links, some of those links will not be available.
  • For the image processing I am downsizing the Wikipedia page images and converting them to monochrome. This works ok for simple images, like flags, logos, even some portraits look decent. However, many images are not recognizable. I’ve been playing with vectorizing the images using line detection algorithms, but have not achieved decent results yet. The problem is that it is very hard to do decent line detection on a 128×48 pixel image for anything other than a very simple image.
  • You may encounter connection issues if you are behind a proxy server or firewall. I originally used a non-standard port (4444), but now use a standard port (23 Telnet) to communicate with the server which should eliminate issues with data providers that block non-standard ports. If it continues to be problematic, I may try to use port 80 directly or even, if necessary, tunnel via HTTP. I would have to write a TRS-80 HTTP client at that point.
  • The rectangular pixel size of the Model I standard graphics mode is causing aspect issues that I have not yet spent time to try to overcome. As a result, images may appear stretched in different directions.
  • Server side sessions get purged after a few hours so if you are browsing longer than that you may encounter erratic behavior and need to restart.
  • You can follow external links out of Wikipedia, but the proxy is not optimized for non-Wikipedia sites so you’re bound to run into issues.

Future enhancements will consist of support for serial port based network adapters.

I used the MRAS assembler from Misosys for development of the TRS-80 client. William Barden’s classic TRS-80 Z80 assembly language books were invaluable in learning to develop assembly programs on the TRS-80.

The proxy server is written in Java and developed using Eclipse. The server runs on an EC2 linux instance running in the the AWS cloud.

Thanks to Pete Bartlett for creating the MISE and providing the APIs and technical support needed to interface with the MISE ethernet connection and TCP/IP stack.

Comments are welcome. This is my first Z80 assembly program so please be kind. 🙂

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