The Custom TRS-80 and Other Mysteries

written by Matthew Reed

Title:The Custom TRS-80 and Other Mysteries
Author:Dennis Báthory-Kitsz
Publisher:IJG, Inc.
Publication date:1982
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The Custom TRS-80 and Other Mysteries is one of the best remembered TRS-80 books. It was written by Dennis Báthory-Kitsz and published by IJG, Inc (also known as the International Jewelry Guild). The first printing sold out in less than a month and the book ended up selling 50,000 copies around the world in three printings. The Custom TRS-80 and Other Mysteries1 (which was volume 3 in IJG’s TRS-80 Information Series) offers an interesting and entertaining look at the hardware and software inside the TRS-80 Model I, the custom TRS-80 of the title.

Dennis Báthory-Kitsz was well known for his TRS-80 writing, including his articles in The Alternate Source and his “80 Applications” column in 80 Microcomputing. (Some of the information in The Custom TRS-80 and Other Mysteries had previously appeared in his The Alternate Source articles.)

The Custom TRS-80 and Other Mysteries was originally supposed to be published in May 1981. However, editorial and production problems on the part of IJG caused publication to be delayed until February 19822. IJG even ran an advertisement in late-1981 titled “Excuses, Excuses…” apologizing for the delay:

IJG would like to apologize to all readers and dealers who ordered the The Custom TRS-80 and have been wondering where it is.

The advertisement further stated “It will be worth the wait, it’s one heck of a book!”


The Custom TRS-80 and Other Mysteries contains eleven chapters and seven appendices. It covers electronics, circuit design, wire wrapping, soldering tips, software, and many other topics, along with discussions of software and hardware products available for the Model I at the time (1981). The book also has many Model I hardware projects for construction, including:

  • a high-resolution graphics modification
  • an interface to a paper tape reader
  • an Exatron Stringy Floppy style storage device created from an 8-track tape player
  • a hexadecimal keypad
  • a hookup for an additional keyboard and video monitor
  • a simple lowercase and reverse video modification
  • a speedup modification for 2.66 MHz or 3.55 MHz operation
  • a method for installing both Level I and Level II BASIC in the same Model I
  • three different real-time-clocks, two with battery backups

Chapter 5 contains the best description of the design problems with the Radio Shack Expansion Interface I have ever seen. Another interesting chapter is Chapter 11, titled “111 Cures for the Common Crash,” which describes 111 (actually 112) tips for diagnosing software and hardware problems with a Model I.


IJG’s bankruptcy in 1986 ended the printing of their books, including The Custom TRS-80 and Other Mysteries3. Montezuma Micro continued to sell copies of it and other IJG books until 1988, by which time they had presumably all sold out.

I’ve always liked the final paragraphs in The Custom TRS-80 and Other Mysteries:

The solons at Radio Shack have done something very impressive: they have created a popular personal computer. From it have come the Models II and III, the Pocket Computers I and II, the Color Computers, the Model 16 is on the way, and a host of engineers around the world have been encouraged to come up with TRS-80 compatible hardware and software, and even full computer improvements like the LNW-80.

But they have done something unwittingly even more special: they have, through strict and strange corporate policies, challenge users to create the Custom TRS-80. Because computers become appliances more and more each day, there will only be one Custom TRS-80 … the humble Model I.

You can download a PDF copy of the first printing of The Custom TRS-80 and Other Mysteries at Dennis Báthory-Kitsz’s website.

  1. IJG also published a book written by Winifred Hofacker and Ekkehard Floegel called The Custom Apple and Other Mysteries. Although a very interesting book in its own right, it was unrelated to the TRS-80 original. ↩︎

  2. The final version of the book still suffers from some production problems, most notably missing figures and tables. IJG also didn’t fix all of the references to figures: for example, “Figure 8-(?)” is referred to more than once. Some of these errors were fixed in the second and third printings. ↩︎

  3. Unfortunately, the IJG bankruptcy deprived Dennis Báthory-Kitsz (and the other IJG authors) of pending royalties, as well as future royalties from sales of remaining copies. ↩︎