Classic Computer Magazine Archive ANTIC VOL. 5, NO. 1 / MAY 1986


Reviewed by Patrick Bass, Antic ST Program Editor


I have a lot of books already, but this volume easily found a place on my reference library shelf. With the exception of VDI and AES information, Abacus has placed, in one package, nearly everything needed for you to start programming the ST. Atari ST Internals has 448 pages packed with information for the user who needs to get work done now.

Abacus has covered nearly every aspect of the 520ST. There are chapters covering all the "off-the-shelf" chips inside the computer. The 68000 processor, 68901 MFP, AY-3-8910 sound chip, WD1772 Disk controller and the 6850 ACIA are thoroughly described, complete with chip pinouts and programming models. But even more important, the book provides detailed examinations of the four custom chips--MMU, DMA, GLUE and SHIFTER.

MMU is the Memory Management chip that controls how the 68000 accesses RAM/ROM memory. DMA is the Direct Memory Access chip which transfers memory from here to there, very quickly. GLUE does just that, replacing many separate ICs with a single package for controlling basic system timing. It literally GLUES the other chips together electrically. SHIFTER is a very fast video-bit shifter that transfers the video information from memory to the display screen.

There are excellent chapters on the different interfaces to the 520ST, including descriptions of the keyboard, mouse systems, video, Centronics parallel port, RS-232 port, the MIDI connection, the cartridge slot, the hard/floppy disk and the DMA interface, along with programming examples for each.

An entire section is devoted to the ST Operating System, and goes into great detail on each BIOS and XBIOS call available. Abacus has even included a section on how to use the "back-door" into the 520ST--the Line-A interface--along with sample programs.

Exception processing is covered in the section that describes the interrupt structure of the 520ST, and gives examples of how to access the Vertical and Horizontal Blank routines already set into the 520ST. The included VT-52 emulator is covered.

Also covered are the known "cast in concrete" system variables down on Page 4. True, Antic introduced these in the September, 1985 issue. But the Abacus book adds sample values and explains what these values mean to the 520ST. Very nice.

Finally, after a short discussion about the 68000 in general, the last third of the book has a printed, commented listing of the Operating System, TOS. I spend most of my time here. Right here in one spot are hundreds and hundreds of programming examples for access into GEM and TOS, written by the same people who brought out the 520ST. (The horse's mouth!)

Them's the picks, now come the nits. Who proofread this book? Zipy the Pinhead? There are so many typographical errors that I stopped counting. The project was obviously rush to print. Also, the programming examples included in Atari ST Internals are in 68000 assembly language, which tells me they assume the reader is familiar with the 68000. Not every one is-- yet. And hey, folks, get this: 448 information-packed pages and NO INDEX in the back of the book. What is this about computer books without indexes? Have we no databases? Nevertheless, this is an important indexless book to have.


If you have a 520ST and feel you need to begin learning 68000 Machine Language (if only to understand the examples in the book reviewed above), you might try ST Machine Language from Abacus.

While other books on 68000 programming are more comprehensive, ST Machine Language not only explains the workings of the 68000, it also gives examples of program code written for, and on, a 520ST. To use the examples in the book you will need a 520ST and practically any 68000 assembler. The assembler in the Atari ST Developers Package or the Haba Hippo-C assembler will work fine.

This book assumes the reader is already programming in a higher-level language (like BASIC or C) and wants to learn 68000 assembly language. It was written, however, so that anyone interested in computers can glean information from it. I admit that my first impression of this book left me lukewarm. But a closer examination, along with the weight of sample programs included, swayed the benefit of doubt over to Abacus' side.

Caveats here include as many typographical errors as in the other two volumes Abacus released for 520ST. (Presenting the Atari ST reviewed in Antic, Octobter 1985.) And don't look for an index in this 277-page book either.

Abacus Software
P.O. Box 7211
Grand Rapids, MI 49510
(616) 241-5510
$19.95 each