Using TEAC 3.5" 720K Floppy Drives In A Rainbow 100 March 26, 1992 INTRODUCTION This document tells how to install a 3.5" 720K TEAC floppy disk drive in a Rainbow. You can install a 3.5" 720K floppy drive in the second drive bay of the Rainbow and connect it to the unused plug (reserved for drives C and D) of the Rainbow's floppy disk controller with a 34-pin cable. But you'll need MS-DOS 3.10B to access it. And if you don't already have a 3.5" I-Drive from Suitable Solutions, you won't be able to format disks on it. There are several parts to this puzzle: the software, the drive itself, mounting hardware, and the cable. SOFTWARE There are two software drivers available to tell MS-DOS about your drive. Both require MS-DOS version 3.10B. IMPDRIVE.SYS is a public domain driver available on CompuServe and from the SF Fido. Suitable Solutions shipped their own driver with their 3.5" I-Drive. The last version was named IDRIVE32.SYS and read three different 720K disk formats. SS also shipped IFORMAT.EXE with their drives, which permitted formatting 3.5 disks. HARDWARE The Drive Suitable Solutions shipped TEAC 3.5" drives in their I-Drive. The part number of this drive is 19307321-12. The model number is FD- 235F, which tells you its a 3.5" double density double-sided floppy drive. TEAC has since replaced model it with part number 19307331-12, same model number. The replacement has a far more elaborate jumper configuration than the old model. To configure the old model, you put one jumper on the pins marked RY and another on the pins marked D1. The new model has a grid of pins running 1-4 on one side, and A-G on the other. The object of the game is to set the drive to respond as Drive 1 (not Drive 0, not Drive 3 and not Drive 4), and to make sure pin 34 is always Ready. To do this on the new drive, you only have to change one jumper from the default PC/AT configuration TEAC ships. Move the jumper connecting pins B4 & C4 to A4 & B4. (See illustration below.) G o o . . o o Represents a single jumper over two pins F . . . . . Represents an uncovered pin E . . . . D . . . . This setup makes pin 34 Ready, and the drive C . . . o respond as D1 B o o . o A o o . . 1 2 3 4 Confirm that the drive will respond as D1 by making sure there's a jumper connecting pins B1 & C1. You'll see a few other jumpers, which you can leave alone. Just for your information: A3 & B3 HA set for 1MB mode fixed. G3 & G4 REN set to enable auto-recalculation. FG Short between FDD frame and DC 0V. Should you buy a TEAC with a different jumper board, you can get the spec sheet faxed to you from TEAC America: 213 726-0303. Mounting Hardware The 3.5" drive needs a 5.25" frame. TEAC kit MF-520 includes a shorter frame than that found on the I-Drive TEAC, screws, power cable, and a short extender board. If you are installing just this drive, you'll need some sort of rail. If you are installing this piggyback on a hard drive, you'll need to fix the 5.25 frame to the hard drive. JDR Microdevices sells such a thing for $2.95. Or you can use your imagination. In either case, you must be sure to cover the whole opening in the Rainbow drive bay. If you don't, air flow over the motherboard will be disrupted and you'll overheat chips, shortening their life. Use a half-height bezel if you just have the 3.5" drive. Hard disks come with their own bezel. If you are replacing an old I-Drive, use the mounting frame from the older drive. The shorter frame makes it hard to connect the ribbon cable (it's deeper inside the housing and you have to unfold the cable and give it a twist), and the bezel is a little taller. You can certainly use the new frame, if you prefer. The Cable The extender board connecting old TEACs to the ribbon cable had one jumper on it labeled ST/OP. In the ST position, pin 34's status was available to the controller; in the OP position, pin 34 was cut off. Just turn the board over to see for yourself. Note that the slot to orient the edge-connector correctly is on the LED side of the drive (not the button side). That's because the board reverses the pins. New TEACs include an extender board, but it's much smaller, does not include the pin 34 jumper, and does not flop the pins. The edge-connector slot is consequently on the button side of the drive now. If you use this extender you'll have to twist your cable to mate correctly, contrary to anything else you may have read. In short, trust the slot. The extender board is optional (at least on the new model). You can connect the cable directly to the drive if you have a long enough floppy cable with pin connectors (like that supplied for a second set of RX50s) rather than an edge connector. Otherwise, Radio Shack sells the parts you need to make the cable: a 34-pin edge connector, a 34-pin plug (similar to the one on the Rainbow's floppy cable), and 34-pin cable (blue with blue and red stripes). Make sure to connect the supplied power cable to the power cable on the Rainbow power supply. The cable is notched so you can't connect it incorrectly.