DVI2nd.INF Adding a second disk drive to the DVI & using THREE sides!!! INTRO ===== Shortly after I purchased my DVI, I realised 166.5K just wouldn't cut it, so I sought out a second drive. Not wanting to pay $260 (plus 75% tax) for the 2nd drive, I asked my hardware hacking buddy what he thought about it, and this article is the result of my endeavor. Normally, adding a double sided drive to the DVI would yield an expensive single sided disk drive. By using a SPST switch a manual side select can be implemented. Unfortunately, to use the second side would require the operator flip the switch under prompts from the program. A better solution is to use a micro-jack (the same size as is used on the REM jack on the cassette cables), and plug the REM plug into the jack. (Some of you can see where this is leading to.) Now, we can access the second side by using the "MOTOR" commands. We will discuss how this is accomplished momentarily. What we are doing here is selectively enabling side 0 and side 1 of the 2nd drive. Under normal conditions, side 0 is enabled, and the heads are moved back and forth under commands from the controller. If we were to disable the side 0 head and enable the side 1 head, we will be accessing the second side. The easiest method I found to accomplish this is what this article is all about. IMPLEMENTATION ============== *** WARNING *** BY PERFORMING THIS PROCEDURE YOU WILL VIOLATE AND VOID YOUR WARRANTEE. PERFORM THIS PROCEDURE AT YOUR OWN RISK. I CANNOT ACCEPT ANY LIABILITY FOR ANYONE USING THIS PROCEDURE. Parts required: 1 sub-miniature jack 1 Shugart SA455 DS drive (or equiv) Wire (hook-up, fine) 4 Screws (for mounting drive) Tools required: Soldering iron Solder, fine, electronic grade Phillips head screwdriver Drill & bit Magnet Procedure: 1. De-energize the DVI IAW DVI procedures. Disconnect the DVI from the M-100/T-200. Place the DVI where you can work on it. 2. Open DVI case. 3. Remove front cover. 4. Insert SA455 in lower slot. Locate mounting holes, mark, and drill holes in DVI lower case structure. This step will require patience. Exercise caution when drilling - maintain control over the filings. Collect filings using the magnet. When you are satisfied the SA455 is securely mounted, remove the drive. 5. Locate terminal pads #34 and #12 on the drive edge connector. #12 is side 1 enable; #34 is side select; by tying these two together, the DVI will access the back side, thinking it's the front side of drive 1:. 6. Solder two wires to pad #34 and #12. These wires should be long enough to reach the jack installation point you have selected from the edge connector with the drive installed. I selected as the location of the jack the front of the DVI, about 1.5" below the POWER LED. NOTE: THE JACK MUST NEVER COME IN CONTACT WITH THE METAL CASE OF THE DVI. EXTENSIVE DAMAGE MAY RESULT TO THE DRIVE CONTROLLER. For this reason I chose the front as it is plastic. Also, by using the front, a small cable can be constructed to control the second drive. See final comments. 7. Connect to the other end of these wires the jack. 8. Install drive, connect power and data connectors. Use caution - DO NOT FORCE CONNECTORS. The data connector is keyed, so it will connect in only one direction. 9. Route jack wires to selected mounting point. Drill hole and mount jack. Ensure wires do not interfere with moving parts of either drive. 10. Secure drive using bolts. 11. Check all connections for tightness and integrity. 12. Reconnect computer to DVI and power up system IAW DVI procedures. 13. Connect your cassette cable to the computer, and the REM plug to the jack. 14. Test operation of 2nd drive: A. Use system disk. (Supplied with the DVI unit.) B. RUN"0:FORMAT" C. Format drive 1: - there should be no errors. If there are, re-check your construction against this procedure. D. LOAD"DNAME" (previously downloaded from DL4) E. Edit line 200: 200 DSKO$1,1,13,1,A$ F. Edit line 300: 300 LFILES 1: END G. SAVE"DNAME" and then RUN H. Name this disk "Side A" I. MOTOR ON J. Format disk 1: again. K. RUN"DNAME" (again) L. Name this disk "Side B" M. MOTOR OFF N. Type: CLS:LFILES 1:MOTOR ON:LFILES 1 You should see: SYSTEM VER MM.DD.YY Side A 166.5 K AVAILABLE SYSTEM VER MM.DD.YY Side B 166.5 K AVAILABLE Ok 15. This completes system checkout. COMMENTS ======== For the cost of a double sided drive (I paid $150) and a jack ($2 MAX) you can have a DVI running three drives!!! (The factory single sided, and the double sided drive.) Granted, there is one major disadvantage: You have to select which side to use with the MOTOR command (OFF -> side A, ON -> side B), which can make programming a little tricky or tedious, but you save over $100, and get twice the drive. Since my ultimate goal here was to create a system to run a small BBS on, and I'm fairly proficient at programming, I can accept the tradoffs involved. (I KNOW where my files are - so it's no big deal to select side B to get a file, then select side A for another file. Prior Proper Planning will clearly reduce the adverse effects of selecting sides.) Once again, for 60% of the cost of a 2nd drive from Tandy. you can TRIPLE your disk storage. And if your clever, the judicious use of DSKI$ and DSKO$ will allow you to recover the two inside tracks on both sides of the 2nd drive, for an added bonus of 4 more usable tracks (8K per side). Now who can't use an additional 16K of disk space??? By obtaining the cassette connector, a sub-miniature plug, and a small amount of wire (2 lead), a cable can be constructed to control the 2nd disk, instead of tying up you cassette cable, or having 3 feet of cabling laying about looking untidy. See following diagram for pin connections: /---v---\ Pin # Function / 7 6 \ 1 Remote | 8 | 2 GND |3 1| 3 Remote | 5 4 | 4 Receive data \ 2 / 5 Transmt data `-------' 6 GND 7 No Connectn 8 No Connectn Connect cable to pins 1 and 3 for remote plug. Abbreviations used: IAW - In Accordance With MM.DD.YY - Current date. Capital Letters - Either a warning, a filename, or what you must type in. The previously mentioned friend and I put this project together (including interruptions, and one mistake) in about 3 hours. The interruptions were phone calls, and our mistake was in trying to mount the jack in the back of the DVI - mounted in the metal cabinet. Fortunately we realised what we did, and averted any trouble. Also included in this time was hooking up a switch to see if this idea would work. When it did, we proceded to the REM jack idea. All-in-all, it went fairly smoothly, with no hangups. As a matter of fact, it took longer to type up this article than the entire project took to build and verify operation. One final word of caution - If you don't feel confident in the disassembly of you equipment, or are hesitant, or have ANY doubts/reservations, by all means, DO NOT ATTEMPT THIS PROCEDURE. If you still desire the advantages previously described, then seek out someone who is competent in hardware manipulations, and employ their help. Even if you have to return a favor, or pay for labour, it is far better than the repair bill to fix the DVI. Oh by the way, there is NOTHING to prevent you from buying the same (or similar) drive, mounting it, and using it as a single sided drive. It will still be cheaper than a Tandy drive and it just plugs in (two cables). And you can still make this mod at a later date if you wish. If you are careful and patient, you can have a very professional looking installation. Maintenance/Operations Considerations: Problems you will encounter with this set-up: ONE: if you want to backup the back side of drive 1:, you'll have to copy it to drive 0:, then copy drive 0: back to the drive 1: backup disk. An alternative to this is to write a short program to backup drive 1: to drive 1: using disk swaps. Or maybe change out drive 0: with a double sided drive modified similarly to drive 1: and using a DPDT relay controlled by the REM plug. (This may be my next project. The concept of a 744K DVI is rather exciting. Anyone want to buy a factory drive 0:?) Another alternative is to move the data connectors such that the single sided drive becomes drive 1:, and the double sided is drive 0:. Using this scheme, BACKUP.SNG (and MOTOR ON) will backup the backside of the double sided drive. TWO: If you use a single sided disk in the double sided drive, and had previously issued MOTOR ON, and then try to access the disk (LFILES 1, or whatever), the system will continue to try to read the directory and hang. I received an interesting error message from this experience. Escape from this by repeated [BREAK]'s & [CTRL][C]'s or by inserting a double sided formatted disk and ignoring the error message. Any comments would be appreciated, but considering my job requires me to leave the U.S. periodically for about four months at a time, I may not receive your comments. Later... +-------------+ | | | Robert Toft | | [74716,476] | | | +-------------+