Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83; site eneevax.UUCP Path: utzoo!watmath!clyde!bonnie!akgua!whuxlm!harpo!decvax!genrad!panda!talcott!harvard!seismo!lll-crg!gymble!umcp-cs!eneevax!ravi From: ravi@eneevax.UUCP (Ravi Kulkarni) Newsgroups: net.micro.atari Subject: 5 1/4 inch floppy conversion for ST Message-ID: <361@eneevax.UUCP> Date: Mon, 9-Sep-85 20:41:01 EDT Article-I.D.: eneevax.361 Posted: Mon Sep 9 20:41:01 1985 Date-Received: Thu, 12-Sep-85 08:48:46 EDT Distribution: net Organization: U of Maryland, EE Dept., College Park, MD Lines: 258 I am forwarding this from the info-st developers mailing list. I have not tried this upgrade but have no reason to think it would not work. -ravi =============================================================== Date: Fri, 30 Aug 85 12:21:57 edt From: Gyorgy Fekete Message-Id: <8508301621.AA05765@eneevax.ARPA> To: info-st Subject: 5.25 Floppy on the ST. Status: RO From: allegra!decwrl!dec-rhea!dec-cgvax2!boiko (Michael Boiko MKO2-2/KO2 264-3626) Permission to reprint or excerpt is granted only if the following line appears at the top of the article: ANTIC PUBLISHING INC., COPYRIGHT 1985. REPRINTED BY PERMISSION. HOW I MADE AN IBM-ST (ST WITH 5 1/4" DISK ACCESS) By DAVID SMALL You can read and write IBM PC disks on your Atari ST -- if you connect a 40-track 5 1/4-inch disk drive to your 3 1/2-inch disk drive. Or...if you don't need IBM file compatibility for an ST, you can connect a 2-sided, 80-track, 5 1/4-inch drive and store 720K on one disk. This will save you money because 5 1/4-inch disks and drives are cheaper than 3 1/2-inch disks and drives. But can you use the disk drive from your 8-bit Atari? Not if the drive is an 810, 1050, or an Atari workalike such as an Indus, Astra, or Rana. However, ATR8000 and Percom drives will work. They are "industry standard" drives that communicate via standard 34-pin interlace connector. THE WARNING Before actually telling how to hook up a 5 1/4-inch drive to your ST, we must caution you this is no job for electronics beginners. You need to solder and to understand the circuitry of whatever 5 1/4-inch you are using. Debugging your new system can be a frustrating experience. Not only that, open up your ST drive and you'll violate the warranty. RIBBONS AND PINS Of the 34 pins in the standard industry connector, only about 14 are used. The Atari ST brings these 14 wires out in a short, thick cable that plugs from the ST into the first drive's IN connector. This cable uses a non-standard 14-pin DIN connector, but it carries industry standard signals. Our goal is to get those signals to a standard 34-pin connctor and thus to a standard disk drive. Theoretically we'd put a 34-pin edge connector on one end of a ribbon cable, 14-pin DIN connector on the other, and we'd have our disk drive cable. However, in practice I couldn't find a 14-pin DIN connector. INSIDE THE DRIVE Therefore, the method I chose to use was to tap into the signals inside the 3 1/2-inch ST drive. Besides voiding your warranty, this will probably require you to cut a slot in the drive case for the new ribbon cable. If you open up the drive (use a phillips screwdriver) you'll find the 14-pin DIN connector expands to (Surprise!) an industry standard 34-pin ribbon cable. Of course, it does this inside the shield to prevent radio noise from leaking out. A small circuit board has the two 14-pin connectors (IN and OUT) mounted on it, and it connects to the 34-pin ribbon cable inside the drive. I put a "tap" from the 34-pin ribbon cable in the drive to the 34-pin ribbon cable running to my remote 5 1/4-inch disk drive. I then used a DB-40, 40-pin male and female clamp-on connector to clamp one side to the ribbon cable and the other to the remote drive's cable. Then I plugged the two DB-40s together. You don't have to use a DB-40. Any clamp-on connector that covers the first 34 pins will work fine. KINKY WIRING But there's a catch. Atari does something kinky with the drive B select signal. It's on pin 6 of the DIN connector when coming from the ST. But inside drive A it is switched from IN connector pin 6, to OUT connector pin 5, where it becomes drive select for drive B. This means Atari ST drives always listen on pin 5 for select, and the daisy chain scheme gives the proper drive the correct signal. Thus the two connectors on the back of the ST drive are not interchangeable, like other Atari drives. Plug your ST into the OUT connector, the drive won't work, period. Therefore we have to jump from pin 6 of the DIN connect (drive B select) to pin 12 of the ribbon cable (drive B select) to get this signal across. Otherwise it doesn't show up on the 34-pin cable otherwise. This is easy to do on the bottom of the 3 1/2-inch drive's DIN connect board. Now we need to set the remote drive as drive B. Sometimes it's called drive 1 or drive 2, depending on whether the manufacturer numbers drives at 0 or 1. When a drive is idle, a five-volt signal (HIGH) exists on the BUSY line. When the computer wants to access the drive, it pulls down this signal to zero (LOW).When the computer is finished with the drive, it releases the signal and the drive "pulls up" the signal to its original five volts. If two drives are hooked up, only one may contain pull up circuitry because the computer can only pull down five volts. Pull-up circuitry usually is contained in a chip in the drive. And now you are at a point where you must know enough about your 5 1/4-inch drive to figure out where the chip is. Since the ST drive A contains all the pull-up termination circuitry we need we must remove termination packs from the remote drive. In the case of my Tandon TM-100-2 drive I also needed to deal with the select line termination, since it doesn't go through the resistor pack. I had to clip resistor R14 from my Tandon to get rid of the added termination. Special Note: The ST monitor throws out a lots of magnetism. If you don't keep your drive at least one foot from the monitor, the disk's heads will pick up the monitor's signals and confuse he read data. You'll immediately notice data error if you get your drive close to the monitor. This is good reason to use a fairly long ribbon cable (3 feet or so) (We haven't noticed this problem in-house. ANTIC ED) ALL DONE All right, assume you have added an 80-track drive. Put the disk in, close the door and turn on the system. Click on drive B, select FORMAT, and format the disk either single-sided or double-sided. >From then on, treat the 80-track drive as an Atari ST drive. Note: 80 track drives have traditionally been persnickety, which is why 40-track drives remain popular. Keep a sharp eye on the drive's alignment. It takes very little misalignment to make a disk that only one 80-track drive in the whole world can read. If you've added a 40-track drive, you may use it as an ST drive in only a limited fashion. You can't use FORMAT or a track copy, because they'll try to force the drive past its 40th track. IBM ST On the other hand, you can put an IBM PC disk in that 40-track drive, and click on the B icon. It'll pull up the disk's directory into folders and "text only" files. You'll notice on the top of the window an PC-DOS type of "pathname" consisting of multiple (if needed) folders and a file name. GEM simply turns the concept of pathnames into folder icons and moves you through the path by your actions of selecting, opening, or closing a folder. Of course, you can't run IBM programs because they are written in IBM assembly language, which the ST cannot understand. However, you can freely copy and use text files and the data within them. Furthermore, if you write back out from the ST to the PC disk, you'll find that an IBM has no trouble reading what you wrote. ================================================================= -- ARPA: eneevax!ravi@maryland UUCP: [seismo,allegra]!umcp-cs!eneevax!ravi