The custom TRS-80 & other mysteries. (book reviews)

The Custom TRS-80 & Other Mysteries, by Dennis Bathory Kitsz. IJG Inc., 1260 West Foothill Blvd., Upland, CA 91786. 335 pages, paperback $29.95. 1982.

In their three previous "Mysteries" books, IJG revealed as much as possible about what goes on inside the TRS-80 and how to get the most out of it. This fourth Mysteries book involves actually getting inside the Model I TRS-80 and modifying it in various ways, and is not for the butterfingered or faint of heart. Page 2 warns that modifying a TRS-80 will void the warranty, and that "modifications are done at your own risk."

If you get past the warning, pages 8 and 9 list the tools you will need, from a screwdriver to a drill. If you feel comfortable using such tools on your TRS-80, go on to the first chapter, which is all about Getting Inside, written very simply at first, but by page 25 getting into masking out the interrupt, with an explanation that is simple enough for bright readers; this is the beginning of power-up routines in assembler, some knowledge of which certainly wouldn't hurt here.

Subsequent chapters (which have no names) get into areas such as number systems, wire-wrapping techniques, software mods (keyboard debounce, machine language monitor, etc.), simple mods (adding 16K memory, adding an extra keyboard, reverse video), adding a HALT instruction, fixing relays, adding hi-res graphics, interfacing the TRS-80 for making music and control, adding a printer interface, adding an 8-track mass-storage system and, now that you have broken your TRS-80, how to repair it, with all sorts of diagnostic programs and scope photos.

The book ends with lists of parts suppliers, bibliography, reference publications, byte values and their equivalents, and IC pinout diagrams.

This book is for the few who are rather bright and who really enjoy digging into the innards of the Model I TRS-80, unafraid to unscrew, cut, solder, drill and otherwise modify their machines.

Review Grade: C