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Text File | 1991-07-30 | 12.2 KB | 276 lines

Dual KickStart ROM Switch Plans Version 1.0 (July 30, 1991) Copyright (C) 1991 by Darren Ewaniuk ----------------------------------------------------------------------------- Description: This is a simple hardware project that will allow you to switch between two KickStart ROMs. With this switch, you will be able to choose to boot from a 1.3 or a 2.0 ROM with a toggle switch, thus gaining the nifty features of KickStart 2.0 while retaining the compatibility of 1.3 if you need it. ----------------------------------------------------------------------------- Requirements: Any Amiga with a 40 pin DIP ROM. Stock 2500's, 2000's, and 500's have this style of ROMs. Some hacks for the 1000 that allow a standard 2000 style ROM for Kickstart are also suitable for this project. ----------------------------------------------------------------------------- Contents: RomSwitch.Doc This text file describing the project RomSwitch.IFF The IFF file showing the schematic diagram RomSwitch.Draw The Draw 2000 CAD file which generated the IFF file RomSwitch.Draw and RomSwitch.IFF are pretty much the same thing, but hey I like CAD programs, so I included the Draw 2000 CAD file for kicks. ----------------------------------------------------------------------------- Parts List: Radio Shack Quantity Description Part Number 1 - 40 Pin DIP socket (preferably with FLAT leads) 276-1996 1 - DPDT double pole double throw toggle switch (preferably one which does NOT have a centre stop) 275-636 4 - Lengths of wire around 60 cm (2 ft) long Don't ask me (preferably a 4-conductor flat ribbon cable) its just wire 2 - KickStart ROMs (1.3 & 2.0 or 1.2 & 2.0) HAH! ----------------------------------------------------------------------------- Construction: First, you should open up your computer and pull out your old 1.2 or 1.3 ROM. Remember which way the notch points, so you can put in your dual ROMs back with the same orientation. In a 2000 class machine, the notch should point toward the back of the computer. You don't need the second (2.0) ROM right away, as this project will leave a socket on top of your old ROM for plugging in the new ROM when it becomes available. This way, you'll be ready for the big moment when 2.0 gets released. (Please let it be soon! :-> ) 1. Select your cheapest ROM (1.2 or 1.3) for the bottom ROM. Find pin 10 on the ROM (Find the notch on one end of the ROM. Orient the ROM so that this notch points towards the back. From this notch, start counting from the left of this notch in a counterclockwise fashion) Gently bend this pin 10 out until it points away from the chip straight to the left. 2. Bend pin 10 of the DIP Socket the same way. 3. Put the DIP socket on top of the ROM with the bent pin. Make sure that all the pins line up and touch each other, except for the bent pins. Press-fit into place, and solder each pin of the socket onto the corresponding pin of the ROM, except for the bent pins. You don't need much solder, just enough to be sure that they won't come apart. Don't spend too much time on one pin, as you don't want to fry the ROM with too much heat. (This is the reason that you want to do this with the cheapest ROM!) Make sure that no solder connects adjacent pins. 4. Now to make the cable. To make things neat, you will probably want to make the cable come from the ROM chips toward the back of the computer to get to the switch. Split the cable for about 7.5 cm (3 inches) with two of the wires going to the left of the chip to the bent pins, and two going to the right to pins 21 and 30. Cut 2.5 cm (1 inch) off all the wires except the one going to pin 30 to make a neat package. Then strip both ends of each wire, and both ends of two of the scraps to use for the switch. Tin all the ends of the wire with solder so that they will stick faster when soldered to the ROM and switch. 5. Now to the switch. It should have two rows of three contacts each. First, connect each corner pin to the pin diagonally opposite it. Solder into place. Then, solder the wires from your cable to the appropriate pins on the switch. The two wires that will go to pin 10 on each ROM should be connected to the two centre pins, and the wires that will come from pin 21 and pin 30 should be connected on the adjacent pins on one end of the switch. The exact pins that these two pairs of wires are connected to do not matter, it just determines which position on the switch turns on which ROM. By looking at the diagram, you should get a better idea of this. 6. Once you have the switch, cable, and socket assembly built, all you have left is to connect them. With a minimum amount of bare wire on the ends of your cable, connect the appropriate wires to pins 21 and 30 of the socket. Make sure these wires do not touch any adjacent pins on the socket. Then connect one of the wires from the centre of the switch to the bent out pin 10 of the ROM, and the other wire to the bent out pin 10 of the DIP socket. Make sure that these do not touch each other or any adjacent pin on the socket. 7. Decide on where to mount the switch. For a 2500 or 2000, I would recommend removing one of the Zorro/IBM card covers, and drilling a hole to mount the switch on that. Then it will be easy to remove the switch and still have no holes in your case. Don't ask me where to mount a switch on a 500 or 1000 though. 8. For easier identification, mark the end of the ROM/Socket assembly that has the notch on it so that it will be easy to identify the orientation that it should be installed, and which way the 2.0 ROM should be oriented. The notch of both ROMS and the notch on the motherboard should all be on the same end. ----------------------------------------------------------------------------- Installation: 1. Take your socket assembly, and gently push it in the ROM socket on the motherboard. Make sure that the notch on the ROM and the motherboard is on the same end. As with all IC installations, make sure that no pins are bent under or splayed away from the socket. 2. Mount the switch in your desired mounting location. Make sure that no bare wires are touching anything, and that the switch is not shorting on anything either. 3. Once you get the 2.0 ROM, install it in the socket assembly that you made up. Ensure that it is oriented correctly, with the notch pointing in the same direction as the ROM underneath and the motherboard. Again, make sure all pins go in the socket, rather than under it or off to the side. 4. Close up your computer. You're finished! Taa-daa! ----------------------------------------------------------------------------- Usage: Easy! With power off, move the toggle switch all the way up or all the way down (or sideways if thats the way its mounted) to select which ROM to use. If you didn't follow my advice and got a switch that has three positions with one in the middle, make sure that it isn't in the middle position. Then turn the computer on and voila! ROM switcher a la Darren. ----------------------------------------------------------------------------- Limitations: If I were you, I wouldn't toggle the switch when the computer is on. Who knows what the system would do when the ROM code changes in the middle of things. That, and for a few microseconds when the switch is in the middle, neither or both ROMS might be selected. Don't muck with the switch with power on and you'll be fine. ----------------------------------------------------------------------------- How it works: The way these ROMs work is that they have two pins that control when they are used. The Amiga uses the Output Enable pin (OE*) to tell the ROM when it wants to access the ROM. In a standard Amiga, the other pin, Chip Select (pin 10) is at 0 volts. If this pin (CS*) is at 0 volts (ground), then when the Amiga selects the Output Enable, the ROM will activate. If this pin is at +5 volts, then the ROM can never be selected and will not interfere with any operations (all outputs will become tri-stated). This switch basically disconnects the normal 0 volts from the ROMs, and puts +5 volts on the Chip Select pin of one ROM and 0 volts on the other ROM's Chip Select pin, thus selecting only one of them. Flipping the switch reverses this, applying 0 volts on the first ROM and +5 volts on the other, selecting the other ROM. These +5 volt and 0 volt signals are obtained from pins 21 and 30 of the ROM chip respectively. ----------------------------------------------------------------------------- Revision history: 29-Jul-91 - Creation date 30-Jul-91 - Version 1.0 First public release ----------------------------------------------------------------------------- Disclaimer: This project works to my knowledge. However, I am not responsible for anything that happens with this. If you screw up the construction, installation, or even if you followed these instructions to the letter and the circuit blows up your computer, don't blame me! ----------------------------------------------------------------------------- Distribution: These plans are Copyright (C) 1991 by Darren Ewaniuk However, you have permission to distribute these plans and make this project as long as you don't sell it commercially. Selling this project for the cost of parts plus the local equivalent of $5.00US or less is acceptable. If you distribute these plans, all files listed in the contents must be distributed. Don't leave any out! In short, I don't want others taking credit for or making money from this project, and don't want it to be distributed with missing or hacked up files. Remember that I can waive any of the rules if you talk to me first! I'd just like to plug the fine Amiga user groups out there. Join your local users group, you won't regret it! The local user group here is AmiCUE (Amiga Commodore Users of Edmonton). Meetings are on the third Thursday of every month. Call 469-6694 for more information. Please leave me comments! I'm lonely! :-> ----------------------------------------------------------------------------- How to reach me: MAIL: Darren Ewaniuk Box 1262 Vegreville AB CANADA T0B 4L0 This is my permanent address and will not change, unlike my present address, as I am currently a student. PHONE: (403)452-2658 (until end of December 1991) (403)768-2431 (after December 1991 or if above fails) USENET: ewaniu@ee.ualberta.ca -or- ewaniu@bode.ee.ualberta.ca (until end of December 1991) darrene@ersys.edmonton.ab.ca (after December 1991 or if above fails) BBS: I can be reached through Devil BBS in Edmonton AB CANADA. I'm NOT the sysop here, but I do frequent this system. My user name is (naturally) Darren Ewaniuk. Its a very nice BBS with over 300 megs of Amiga files. If its near you or if you don't mind long distance, try it out! Devil BBS Sysop Basil Barnes (403)484-9200 Running on an Amiga 2500/30, with USRobotics Dual Standard HST/V.32/V.42 capable modem and multi-serial card. All Amiga files, over 300MB storage, running Skyline software. Freely distributable software only - no pirated stuff here! ----------------------------------------------------------------------------- _________ _________ This is | | This is | | DON'T DO IT! your | O O | your | x x | computer | + | computer | ___ | Just say NO! | \___/ | on pirated | / U\ | ___ to piracy |_________| software |_________| \ _________ _ _________ _ \[Computer sick |[][][][][| |_| |#&%@!%$&!| |x| with a virus] |][][][][]| | | /|^!*%@&*@#| | |\ |_________| |_| [Nasty words] |_________| |_| [Dead mouse]