Welcome to the Model I System Expander (MISE) Project!


The MISE (Model I System Expander) is an add-on device for the vintage Radio Shack TRS-80 Model I microcomputer. It connects to the buffered expansion port on the Expansion Interface or directly to the Model I keyboard, and provides these benefits:

The AC adapter (US-style plug, UL-listed) needed to power the MISE, and the ribbon cable to attach the MISE to the Model I, are both included.

Minimum system requirements: TRS-80 Model I Level II with 16KB RAM; see Using the MISE with only 16KB RAM or without an Expansion Interface for more information. The Level II ROMs' floppy boot code must not have been modified or relocated.

Highly recommended: Expansion Interface, 32KB total RAM.

Suggested: At least one floppy drive, 48KB RAM.

To fully utilize MISE: SVGA capable monitor and VGA cable, CAT5e or CAT6 Ethernet cable and network connection, Atari 2600 compatible joystick.

To reprogram the MISE FPGA with updates: USB Blaster or Byte Blaster II (parallel port), and free Quartus II Web Edition software from Altera installed.

Product Pricing

Price list


December 18, 2022: From now on, MISE units will be shipped with single-sided IDE/CF adapters, because I can no longer obtain the reverse-side CF sockets. This means that you can have one CF card acting as a primary IDE drive, but no secondary IDE drive. The preferred backup solution is to dump a raw image of your CF card to your PC using a CF card reader/writer device, and restore the image directly to the CF card should it become necessary.

March 26, 2019: The new MISE version 1.2 PCBs are in, and units are being assembled to order. This revision is functionally identical to MISE 1.1, but has several physical changes... the most noticeable being that the boards are black instead of green.

September/October 2017: MISE, M3SE, and MIRE at VCF Midwest 12 and Tandy Assembly!

24 December 2016: I'm happy to announce a price decrease on MISE units, due to lower production costs.

10 September 2016: MISE and M3SE at VCF Midwest 11!

7 June 2016: The FTP client and the Ping utility have been added to the regular file archives and will be included with all future MISE deliveries.

30 August 2015: MISE at VCF Midwest 10!

In these photos you can see maybe one quarter of the main exhibit room. Many, many people stopped by during the show to take a look, play some games, and ask questions about MISE.

The Model I in the center has the MIRE (Expansion Interface replacement project) prototype attached. The Model III has the M3SE (MISE for Model III) prototype attached.

Thanks to Malcom Ramey for supplying most of the hardware in the exhibit.

25 July 2015: I've filled most of the MISE pre-orders and have started putting units (one by one) on eBay. The eBay price is $350 including U.S. shipping. International shipping is extra.

If you contact me directly rather than buying on eBay, the price is $330 including US shipping.

20 July 2015: New batch of PCBs is in. Will start building them out when work on the M3SE (subset of MISE for Model III) and MIRE (Expansion Interface replacement) allows. Shoot me an email if you want to obtain a MISE.

Here are some demo videos of MISE 1.0 in action. Since you're here, you already realize that the URL given at the beginning and end of the videos is obsolete:

Customer Photos

But What Can I Do With It?

Well, how about browsing Wikipedia with Peter Cetinski's TRSWiki project?

Or, you could connect to host computers around the world using the Telnet client and 80-column display mode:


Here's a PDF of the documentation thanks to Richard Zimmerman.

Setting up the MISE

Network Configuration

Network Applications

Network Demos

Making MISE system floppies

Compact Flash Hard Disks

Using the VGA display

Using the real-time clock/calendar

Using the joystick port

256-byte general-purpose EEPROM

Using the ROM-based double-density floppy disk adapter driver

MISE feature control registers

Utility programs

Installing FPGA updates

MISE serial number

Hardware Errata


Obtaining Software

MISE comes with LDOS-5.3.1 pre-installed, including Matthew Reed's "Year 2012" patches. Roy Soltoff has made LDOS freely redistributable. It is being provided free of charge.

All software needed to use and reconfigure the CF hard drives is included. Some programs are modified versions of the LDOS originals, and some are custom. Miscellaneous other utilities and demo programs, as described in these pages, are also included.

Other software packages you may wish to obtain are copyrighted, so I can't distribute them with MISE. Recommended ones include:

There are many places to obtain this and other software. The following are good places to look:

Planet Emulation

Tim Mann's TRS-80 Pages for Misosys software

Classic Computing

Once you've obtained the software, simply use the FTP server to copy it to your TRS-80.


The MISE Yahoo group!

The TRS-80 Yahoo group where MISE was introduced and is occasionally discussed.

The Floppy Days Vintage Computing Podcast, which often discusses the TRS-80. Pay special attention to Episode 20!

The TRS-80 Trash Talk Podcast.

The Vintage Computing Forums' Tandy/Radio Shack Forum.

arcadeshopper is selling a 3d printed MISE enclosure.


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