uhclem@trsvax.UUCP (10/17/88)
<B> The following information is provided by an individual and is not nor should be construed as being provided by Radio Shack or Tandy Corp. Radio Shack/ Tandy Corp has no obligation to support the information provided in any way. cut here- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 6000 > 4000 > 3000 Vol 1, No. 1 Utilizing 5 1/4" media on your Tandy 16/6000 computer system. 28-Aug-88 by Frank Durda IV (c) 1988 If you have reached the point where you are having trouble getting 8" media, or getting the drives repaired or replaced, this may interest you. The following information will allow you to add or substitute 5 1/4" high capacity floppy drives for 8" double sided drives in your 16/6000 XENIX system. You can mix 8" and 5 1/4" drives, or chuck the 8" drives entirely. If you just want to look at the pay-back, pull out your handy Radio Shack computer catalog. Ten 8" DD DS disks cost $39.95. Ten 5 1/4" HD DS disks cost $34.95. If you buy your disks at those prices, it will take 20 boxes of 5 1/4" vs 8" diskettes to pay off the approx $100 drive. Since most mail order houses can get you ten 5 1/4" HD DS for less than $20, a 5 1/4" drive will pay-back a lot quicker. In addition, most people would agree that 5 1/4" media quality is usually better than the 8" media available today. If you want to add 5 1/4" drives externally, you should obtain an enclosure to mount the drives in. These are available from numerous mail-order houses. One is AEROCOMP, 2544 West Commerce St, Dallas Tx 75212, P.O. Box 223957 and the order number is 1-800-527-0347. (Sorry, I have never done business with this firm, so I can't comment on their product.) They advertise an enclosure for two 5 1/4" drives. You could also order such an enclosure from Radio Shack National Parts (it was used for CoCo drives in recent years). Almost any high-capacity (1.2 Meg) drive can be used. I used Mitsubishi MF504B-347UA drives. For that particular drive, these straps should be set: TD MS SR-PM2 RI SB DSx Other drives that should be acceptable include TEAC 55G series drives. DSx should be set as you prefer. On a Model 16B and 6000 drive 0 may not be selected on the external connector. If you have two internal drives on a 16B/6000 and want to keep using them, your external drives must be DS2 and DS3. The last external drive must contain a terminating resistor pack. If you only have one internal drive, you may have three 5 1/4" external drives. Set the strap DS1 for the first drive, DS2 for the second, and DS3 for the third. If you have two internal 8" drives and you wish to disable one of them, it will be necessary to disassemble your 16B/6000, and disconnect power and data cables going to your second internal drive. If the terminating resistor pack is installed on the drive you are disconnecting, you must move the resistor pack to drive 0. By disconnecting the power, you will reduce the power consumption and heat load on your system. You must also add a jumper at E40-E41 on the main CPU board (under the card cage). This moves the DS1 signal to the external connector. If you have a Model II or 16A, you can have at least two external drives and as many as four if you decide to disable the external drives. Initially it is suggested that you leave drive 0 as an 8" drive until you can copy your installation floppies onto 5 1/4" media. On the Model 16A, 16B and 6000, it is advised that you leave one internal drive connected to power even if you decide to disconnect its data cables. This is to insure a minimum load on certain power supply voltages. You must construct the cable between the Model II/16A/16B/6000 and the 5 1/4" drives. You will need a 50 pin dip connector and at least one 34 pin edge connector (one per drive). You may use either 34 or 50 pin wire. If you have an existing 50 pin cable and a 34 pin cable, you may simply wish to cut the connector off one end and splice the appropriate signals together. Just try to keep the total length to under 6'. Because the cable you build may be delicate, you may want to build it as a short cable which can fit entirely inside your drive enclosure with the 50 pin connector mounted so that a longer standard 50-to-50 pin cable can connect between the computer and the drive enclosure by plugging into the "translation" cable. Here is the wiring table. Keep in mind that the odd numbers are ground on both the 34 and 50 pin connectors. The new cable should re-route the wires in pairs to help simplify assembly and assure adequate ground. When an entire group of wires can be moved as a set, they are listed together. Signal Name 50 Pin tie to 34 Pin connector connector Pins Pins Side Select (14) 14-15 32-33 Index (20) 20-21 8-9 Ready (22) 22-23 34-35 Drive Select 1 (26) 26-31 10-15 Drive Select 2 (28) Drive Select 3 (30) Drive Select 4 (32) 32-33 6-7 Direction (34) 34-47 18-31 Step (36) Write Data (38) Write Gate (40) Track 0 (42) Write Protect (44) Read Data (46) In addition to the above, pins 10 and 11 on the 50 pin connector must be tied together to produce the "double-sided" signal that the Model 16/16B/6000 requires. All other pins on the 34 and 50 pin connector should not be connected to anything. Your cable can look like this: +---+ +-----+ +-----+ ! 5 !--------\ /------! 3 !--------! 3 ! ! 0 !--------\ A miracle/-------! 4 !--------! 4 ! ! !-N/C occurs----------! !--------! ! ! p !------------here-----------! p !--------! p ! ! i !--------/ \-------! i !--------! i ! ! n !-------/ N/C-! n !--------! n ! +---+ +-----+ +-----+ DIP Edge Edge That is all there is to it. Once you have built your cable, and applied power to your drive enclosure, connect the cable to your Model 16/16B/6000 external floppy connector (on the 16B/6000 it is behind the access door and in the lower right corner), and turn on your system. If the drive light comes on and stays on, this usually indicates that the cable is plugged in upside down somewhere (check your pin 1 keying). If the drive light does not light, run diskutil and attempt to format a floppy in that drive. If the drive light does not come on, check the drive select strap on the drive and make sure it is set to the drive number you tried to format. If that is ok, the cable may be at fault. If the drive light does come on but diskutil does not get past cylinder 0, the terminating resistor may not be installed or the cable is incorrectly wired. If diskutil gets all the way through formatting a floppy, and it behaves as though it formatted a double sided disk, you are in business. If you have some programs that are hard coded to expect media in certain drives under XENIX, consider renaming the device names (/dev/fdn, /dev/rfdn, /dev/fdbtn and /dev/rfdbtn) so that you can use 5 1/4" media instead. Be sure to rename all the floppy devs with the same drive number or else you can get into trouble. Although the 5 1/4" drives are 80 track drives, only 77 of the tracks are used under 6000 XENIX, because it still thinks it is talking to a 77-track 8" drive. However, because 6000 XENIX writes the correct number of sectors per track allowed for that transfer rate and motor speed (16 512-byte sectors), the XENIX-usable storage will equal 1.224 meg ((76x2x16)+16)x512 = 1,253,376, which is 24K more than the IBM AT format allows. The full 80 tracks can be utilized, but this requires patching and more operator intervention when performing tars dumps and file-system creation. This and passing data between IBM AT and a 6000 XENIX system on 5 1/4" disks will be discussed in a future article. One final note: Not all the 5 1/4" disk drives will detect a diskette change as the earlier 8" half-height drives did (most had square lights). (The cost-reduced 8" drives usually had round drive lights and these would only report a disk change if it occurred while the drive light was on.) Because there is no separate signal line available, some 5 1/4" drives simply do not provide that information while others combine it with the READY signal or some other signal. On the drives I used, I found that attempting to use the combined READY and DISK CHANGE caused numerous problems so the above straps do not enable that feature. --- cut here- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - If you have questions about this article, please send email to: Frank Durda IV @ <trsvax!uhclem> ...decvax!microsoft!trsvax!uhclem ...hal6000!trsvax!uhclem
rmb384@leah.Albany.Edu (Robert M. Bownes III) (10/24/88)
Uh, frank, Would your cable modification be equivilant to putting a connector onto the 34pin space provided on the Model II/16 FDC card (No, I don't mean the LPR connector. I mean the one that never had a connector installed at all.) There are jumpers to deal with running a normal low density floppy (I'm not recomending this, just the use of the connector...) off these connectors. bob the ineloquent this am... -- Bob Bownes, Aka Keptin Comrade Dr Bobwrench III | If I didn't say it, It bownesrm@beowulf.uucp (518)-482-8798 | must be true. {steinmetz,brspyr1,sun!sunbow}!beowulf!bownesrm | - me, tonite -