Classic Computer Magazine Archive START VOL. 3 NO. 1 / SUMMER 1988


Let's Twist Again!

by Dave Small with Dan Moore

Increase disk capacity! File TWISTER.ARC on your START disk.

I've always liked tools.

One of the greatest presents I ever got for a birthday was a Sears toolkit. At age 16, I immediately went to work with it, disassembling and (sometimes correctly) reassembling the family cars. While it drove my parents crazy, I learned a lot about cars--and about tools. I've never worried about a car breaking since, because now I know a lot about how cars work, and I have my tools.

When I went to college, I took my toolkit along. Some of the great unsolved pranks at Colorado State have their home in my toolbox. Pliers, socket wrenches, wire cutters, phone-tapping tools. . . The statute of limitations isn't up yet, so I'll pass on mentioning anything else. But none of those pranks would have been possible without those tools.

And I've carried that philosophy forward in my programming career, such as it is. I always try to accumulate tools.

People who've followed my writings know I regard computers as somewhat mystical, troublesome beasts, which break a lot. Sometimes they break for no reason at all. When the computing gets rough, the programmer had better have a well-stocked toolbox.

Hence the thrust of this column: A place to accumulate tools to help you in your ST life.

Incidentally, a tool isn't any good without enough knowledge to use it. Sometimes a little knowledge--let's say, how the hard disk is partitioned--will be enough to help you fix a problem. Knowledge is also a tool, and will be part of this column.

Some tools will be like a torque wrench; you only need them during a major engine rebuild. Some tools will be like a pair of pliers, useful almost daily. And there will probably be tools you'll never use.

But these tools didn't get written for fun. Many of them are from Dan's and my personal toolboxes of disaster fixes. Some of them were written in the heat of desperation; others were written in the bitter aftermath of "I'll never let that happen again."

So, let's open the toolbox.


Back in the Spring 1987 START, we introduced a disk format program known as Twister. Twister formatted disks so the ST could run them at twice the present disk rate. Basically, Twister helped the original ST ROM operating system overcome the delay caused by stepping the head from track to track.

Twister was written as a part of the "megabyte-a-minute" backup program, an exploration of how fast data can be moved from a hard disk to a floppy.

Twister gave you 10 sectors per track, instead of the ST's usual 9. This gave you 40K more per disk side, and at twice the speed! It soon became an alternate disk standard format. There were also some explorations done of extending Twister to 11 sectors per track, and 82 tracks per disk--but those don't give you much reliability moving from one ST to another.

Since then, Atari has issued a new revision of the TOS ROMs, called the "Blitter" ROMs, and installed them in the new Mega computers.

(Why are they named "Blitter" ROMs? Imagine about a thousand independent ST software engineers holding their fingers to their mouth, saying "b-b-b-b-blitblitblit," as they discover their applications don't work on the new ROMs, and they're going to have to do a rewrite. Realistic special effects include moans, rolling of the eyes, and fainting.)

Yep, it happened to us too. Twister and the twister-formatter portion of Meg-A-Minute broke on the new ROMs. The reason? We used a variable that the ST uses to remember the disks' current track number, and it changed in the blitter ROMs. We must tweak this number to get the "verify" portion of the formatter to work.

You'll find the new Twister, along with its source code, on your START Disk in the file TWISTER.ARC. Copy TWISTER.ARC and ARCX.TTP to a fresh disk, double-click on ARCX.TTP, type TWISTER.ARC and press the Return key, and in no time you'll have the new Twister on your disk, ready to use.

As you'll see in the source code, we didn't have to make major changes. A new piece of code looks for the ROM identifying stamp, then directs the Twister routines to the proper memory location.

Using Twister remains the same as before: it simply works on Megas as well as on regular STs. Boot in medium or high res, and double click on TWISTER.PRG. Click on the drive you'd like to format, and how many sides you'd like formatted. Go away while the drive does its thing. Afterwards, it will tell you how the format went. There-after, any floppy access to the Twister-formatted floppy will be very quick.


Next issue, we'll take a look at how fast your drives are spinning--and why it's important.

Dave Small is the creator of the Magic Sac Macintosh emulator and the Translator One disk controller, and the author of three books and many computer articles. Dan Moore is the author of PaperClip for the 8-bit Atari computers.