HOW TO RUN THREE FLOPPY DRIVES IN AN AT-COMPATIBLE MACHINE (without buying another controller card) By: Bob Sully (CIS ID 73545,232) DISCLAIMER: This method is ADMITTEDLY a kluge. It's basically a home- brewed solution to the problem of running 1.2MB, 360K, and 720K/1.44MB floppy drives in a machine (an AST-286) with the standard 2-floppy/2-HD Western Digital controller card and only ONE remaining expansion slot (six being full). It IS possible to run three (or four) floppies in such a machine concurrently with some of the new FDC cards now available. I simply didn't want to spend the money and lose my last slot! This method allows three drives to be used in the same machine, but only two are usable AT THE SAME TIME. Please, don't sue me if this doesn't work in your machine..I can't guarantee it to work in any other configurations. The system is as follows: AST Premium 286 under AST's MS-DOS 3.3, running TEAC 1.2MB and 360K 5.25" and Sony 720K/ 1.44MB 3.5" floppy drives, one inboard 72MB hard disk and outboard 20MB HD. 2M of RAM on the FastRam card and 3MB extended memory on a "clone" multi- function card (all purchased at between $2 and $2.95/chip!). Necessary hardware: (1) 3.5" floppy drive. If you're going with a 720/1.44, get one with the auto-sensing media switch (automatically switches between 720K and 1.44MB disk formats by checking for the hole in the casing on the high- density media). The Sony drive is so equipped. (2) Micro toggle switch (SPDT); cost is about $2.50 at most electronics stores. (3) 34-line card-edge connector. (4) 26-gauge wire. (5) Soldering iron, X-Acto knife (or equivalent), wire cutter/stripper, electric drill, vise (PanaVise type optimal). PROCEDURE: (1) Make sure that your floppy-drive cable is long enough to support three drives. If not, get one that is. Mount the 34-line card-edge connector onto the cable with a PanaVise or similar instrument, leaving enough room between connectors for all three floppies to be properly mounted, and enough cable to reach the floppy-disk controller card. (2) CUT line 12 (drive select line for physical drive 1 (B:) between the new card-edge connector (the first one on the cable when starting from the controller end). Solder a length of 26-gauge wire to the controller end of this line. Solder the other end of the 26-gauge wire to the middle connector (common) of the SPDT switch. (3) CUT line 12 again between the first and second card-edge connectors (from the controller end - NOT between drives A: and B:!). Make sure that the cut ends do not contact each other (otherwise, both the 2nd and 3rd drives would be selected at once!). (4) Solder a length of 26-gauge wire to EITHER each of the cut ends of line 12 from Step (3) OR to finger number 12 on each of the two drives to be switched (the fingers are numbered 2,4,6,8,10,12....on the top of the card edge of most floppy drive; usually they are marked). If you decide to use the card edge, solder as close to the front (towards the front of the drive) as possible, to allow the card-edge connector to make good contact with the card edge. Solder the other end of each wire to one of the two remaining connectors on the SPDT switch. (5) Mount the switch. Most of the 3.5" floppy drives have plenty of room next to the opening on the front panel. Mine is just to the right of the disk-access slot. My drives are mounted with the 1.2M as A: on the top, the 360K in the middle, and the 3.5" on the bottom. The switch in the "up" position selects the 360K, "down" selects the 3.5" drive. (6) Re-mount the floppy drives in the computer, and hook up the cable. (7) Here's where it gets a bit tricky. This set-up works fine on an AST Premium 286, but in other machines there may be some problems. My machine's BIOS is set up to handle 720K/1.44 MB floppy drives. I have mine configured with A: as a 1.2M 5.25", B: as a 1.44M 3.5". I use DRIVER.SYS to create a second logical device on physical drive 1; its designator turns out to be G: in my case. This line goes into my CONFIG.SYS file: DEVICE=C:\SYSTEM\DRIVER.SYS /D:1 /F:0 /T:40 /S:9 /C. When I boot up, the switch is in the "down" position, so the system sees the drives as they are configured under SETUP. When I need to use the 360K drive, I flip the switch up and refer to it as drive G:. So far, under AST's MS-DOS 3.3, I've had NO problems reading, writing, or formatting any of the three drives; I do use a neat little utility called QDR (QuickDiskette Reformatter, available in the public domain) to format Drive G:; PCTools will also format any of the three drives. You MUST have a version of DOS which supports all three drive types, and probably a BIOS which does also, or this probably won't work! (8) I have included in the .ARC file a little batch file I use to format floppies. If you look at it you'll notice that I've renamed FORMAT to TAMROF. This, in addition to the batch file itself, tends to prevent "accidental" formatting of your hard disk. You will also need to obtain a copy of Vernon Buerg's QDR.COM for formatting the third (in this case the 360K) drive. It is in the public domain and is available on CIS and on most local bulletin boards. I am using version 3.2. Happy homebrewing -- Bob