EnigmA Amiga Run 1997 February

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/ EnigmA Amiga Run 1997 February / EnigmA AMIGA RUN 15 (1997)(G.R. Edizioni)(IT)[!][issue 1997-02][PLANET CD V].iso / enigma / earcd / utility / utilhard / a2kgnshk.lha / 2MBAgnushack_v1.3.txt

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Text File | 1997-01-06 | 16KB | 343 lines

A2000 2MB CHIP RAM HACK VERSION 1.3 Permission is granted to freely distributed this document as long as it remains as is. If errors are found, something does not make sense, or something should be explained further, please inform the author immediately. This document has been reviewed many times to ensure that it is accurate. The author is not responsible for damage to your machine as a result of possible errors in the document or mistakes by the person performing this hack. To perform this hack, please follow the steps by number. 1. Verify that this will work with your A2000. To determine this, count the RAM chips. If there are eight, then this hack will work. If you have more than eight, then this hack will not work on your Amiga, and to expand your chip RAM you will have to purchase a chip RAM expansion device. 2. Obtain the parts. One 8372B or 8375B Agnus part number 318069-03. Four 1MB x 4, 80ns or faster DRAM DIPP chips. or Four 1MB x 4, 80ns or faster page mode DRAM ZIPPS and four 20-pin component carriers. See diagram 2 for layout of each. Eight machine-pin 20-pin DIPP sockets. Four are optional. Do not get those cheap sockets at Radio Shack. They will cause you nothing but problems. The best solution would be to solder the chips in the motherboard. If you do not want to risk the chance of burning up your memory, use sockets. One 22 ohm resistor (ideally 25 ohm, but do not sweat finding one). One 470 ohm resistor. One spool wire-wrap wire. One piece 1/8" diameter heat-shrink tubing. Optional: Two AT socket extenders. While you have the motherboard out, you may as well upgrade those XT sockets to AT sockets. I found those extenders hard to find. What I did was to buy two one-piece AT sockets at Radio Shack and used a hack saw to cut off the part I did not need. If you decide to do this, you can solder in the new socket extenders at any time after removing the motherboard. 3. Get the motherboard out of your A2000. If you can not figure this out on your own, then you should not be doing this hack. There are several screws on the motherboard that need to be removed and there are the other critters on each side of each connectors (i.e. mouse, serial, parallel ports) that also need to be removed (If you know the name of these, please let me know). The motherboard should come out fairly easy. Do not force it out, but it may take a little twisting to get out. 4. Remove the shielding and insulation from the bottom of the motherboard. If you haven't already removed those critters mentioned in the previous step, do that now. You will have to bend the shielding a bit to get it off. 5. Remove the eight 256K x 4 memory chips. Use diagonal cutters and clip the leads from the side of the memory chip. Stay away from the motherboard. A careless cut close to the motherboard can clip vital traces. Do not try to save these chips by desoldering them. You will probably damage the mother- board and will more than likely destroy the chips anyway. 6. Remove the leads from motherboard. You can just remove those from chip positions U501-U504 or optionally remove all of them from positions U501-U508. I decided to clean all of them and install sockets in positions U505-U508 in case I wanted to undo my work. If you are lucky enough to have access to a desoldering gun this will be a piece of cake. You can also use a soldering gun and a desoldering pump. A good cheap way to do this is to use solder wick to soak up all the solder from each position and remove the pin. If you de- cided not to install sockets in positions U505-U508, just clip off the excess leads being careful not to cut traces on the motherboard. 7. Install the sockets in the open positions. Install the sockets with the notch facing the same direction as the pattern on the motherboard. Solder each pin being careful not to use too much solder because excess amounts of solder can cause solder bridges to form under the socket. 8. Take the wire-wrap wire, put one end of it on pin 5 of U503, and stretch out enough to reach pin 5 on U502. Cut the wire slightly longer than that distance as you can always remove the excess wire later. Solder one end of the wire to pin 5 of U503. Stretch the wire to pin 5 of U504 and solder it in place. The insulation of wire-wrap wire is very thin and will easily melt off leaving a clean connection. Stretch the wire to pin 5 of U501 and solder it in place. Stretch the last bit of wire to pin 5 of U502 and solder it in place. You can now cut off excess wire-wrap wire. 9. Take a 22 ohm resistor and cut the leads so it fits nicely between pin 4 of U507 and pin 5 of U503. Cover the resistor with heat-shrink tubing and heat the tubing so that it shrinks nicely around the resistor. Trim the tub- ing so that a small portion of the lead protrudes from each end. Solder one end of the resistor to pin 4 of U507 and the other end to pin 5 of U503. This may be a little tricky since the wire-wrap wire is soldered to pin 5 of U503. Just be careful not to allow the wire-wrap wire to come off. NOTE: Ideally this resistor should be a 25 ohm resistor so that when it is placed in series with the existing 22 ohm resistor the total resistance will be 47 ohms. Although a 25 ohm resistor is available, you may have to special order it and it will probably cost more than a 22 ohm resistor. Using a stan- dard 22 ohm resistor will make the total resistance 44 ohms. 44 ohms is close enough and it will not affect the operation of the system. 10. Take a 470 ohm resistor and cut the leads so that it fits nicely between pin 5 of U502 and pin 1 of RP503. Cover the resistor with heat-shrink tubing and heat the tubing so that it shrinks nicely around the resistor. Trim the tubing so that a small portion of the lead protrudes from each end. Solder one end of the resistor to pin 5 of U502 and the other end to pin 1 of RP503. This may be a little tricky since the wire-wrap wire is soldered to pin 5 of U502. Just be careful not to allow the wire-wrap wire to come off. 11. Remove R110 by clipping it free from the motherboard with diagonal cutters. 12. Remove R212 by clipping it free from the motherboard with diagonal cutters. 13. Remove the solder and lead from R212 as shown in diagram 1. 14. Take the wire-wrap wire, Solder it in the hole left from step 13. Take the other end and stretch it to pin 36 of the Gary chip, and clip off the excess so that it will fit nicely in place. Solder that end to pin 36 of Gary. 15. Use a PLCC chip puller to remove the 1MB Agnus from it's socket. Using any other method could damage both the chip and the socket. Selling the removed Agnus can help offset some of the cost of this hack. 16. Insert the new Agnus into the socket. The socket is keyed so that the Agnus chip will only go in one way. 17. Insert the 4 1MB x 4 DRAM DIPPS or the 4 1MB x 4 DRAM ZIPPS mounted on the component carriers in sockets U501-U504. Be sure to insert them cor- rectly. 18. It does not hurt at this time to check your work. If you have access to an ohm-meter or continuity checker, use it. Follow along with the schematics in your A2000 users manual to check correct configuration. It is nearly identical to the way it was before with the exception of the new address line. 19. Assemble your Amiga only enough to test it. Replace the insulation and shielding, insert the motherboard, and attach power and floppy drive(s). Also attach the keyboard and mouse. 20. Power up the system using a bootable floppy disk. Of course you will not have any fast RAM, but your chip RAM display on the Workbench title bar should be close to 2MB. It may be a little less, but that is okay. If it shows 1MB or less, then you have a problem. If you get colored screens, then you have even a bigger problem. If any problem shows up, remove the motherboard again and thoroughly check each and every connection. Also check connections with adjacent connections for shorts. Troubleshooting: If your system only shows approximately 500K chip RAM, then the possible causes are that the memory you inserted is 256K x 4 DRAM, or that the new ad- dress line (A9) is not wired properly. If your system boots with a red or yellow screen, reseat the memory and the ROM chip. Double check the solder connections being sure that they are con- nected and no solder bridges have formed. If you find that you can not get a pin to solder correctly to the motherboard, use wire-wrap wire, solder it to the pin, clip it so that it will reach an- other mounting point, and solder it to that point. This is preferable to over soldering since over soldering could lead to solder bridges which are very difficult to eliminate without removing the chip or socket. Example: When checking address line 4 (pin 11 of the memory chips), you find that it does not connect to U502, but does connect to the other chips. You try again to solder it, but can not get it to connect. Take a piece of wire-wrap wire, solder it to pin 11 of U502, clip the wire to reach pin 11 of U501 and solder it to that pin. 21. If you have 2MB of chip RAM at this point, congratulations! If you plan on using cards that occupy the video slot, perform the additional steps in the section titled "Creating The New Clock Signal", otherwise, completely assemble your Amiga and enjoy the new found chip RAM. Any questions or problems, please e-mail me at kgroombr@hereford.ampr.org Creating The New Clock Signal ****************************************************************************** NOTE: This has not been tested. If you perform this part, it is truly at your own risk, however, I have checked this over and over again, and even plugged it into a program to ensure that the correct signals are produced. If you do this portion, please e-mail me with the results so I can update this document. ****************************************************************************** Cards such as the Video Toaster use clock signals that are no longer present on the 2MB Agnus. 2MB Agnus boards use on-board circuitry to create signals that will allow these boards to work. The circuit can be built and installed by doing the following steps in order. 1. Obtain the parts. One 7400 NAND GATE chip. One 7432 OR GATE chip. Two machine-pin 14-pin DIPP sockets. One prototyping board to hold both 14 pin chips. One spool wire-wrap wire. 2. If not already sized, cut the prototyping board just large enough to hold both 14-pin sockets. The best way is to place the sockets side by side as op- posed to lengthwise. 3. Insert the two 14-pin DIPP sockets into the prototyping board. 4. Use the wire-wrap wire and solder the following connections. SOCKET 1, PIN 2 to SOCKET 2, PIN 2 SOCKET 1, PIN 3 to SOCKET 1, PIN 12 SOCKET 2, PIN 3 to SOCKET 1, PIN 13 SOCKET 1, PIN 11 to SOCKET 1, PIN 10 SOCKET 1, PIN 10 to SOCKET 1, PIN 9 SOCKET 1, PIN 7 to SOCKET 2, PIN 7 SOCKET 1, PIN 14 to SOCKET 2, PIN 14 5. Now the tricky stuff. Since I have not done this, you will have to figure this out on your own. Cut the trace that leads to pin 36 of the Agnus chip. Do not cut very far away from the Agnus chip since the are other circuits in the Amiga that feed on this signal. You better make sure that you are cutting the correct trace before doing this, so I emphasize to triple check this! Have a friend check it too! After cutting this trace, tie pin 36 of the Agnus chip to +5v. Pin 15 of the Agnus is +5v. 6. Now more tricky stuff. Cut the trace that leads to pin 34 of the Agnus chip. As in the previous step, ensure that you are cutting the correct trace. Also, do not cut very far away from the Agnus chip since the are other cir- cuits in the Amiga that feed on this signal. 7. Use the wire-wrap wire and solder the following connections. SOCKET 1, PIN 1 to the trace that was cut away from pin 34 of Agnus. SOCKET 2, PIN 1 to the trace that was cut away from pin 36 of Agnus. SOCKET 1, PIN 2 to the empty hole where R212 was cut away. The other hole has the jumper to Gary. SOCKET 1, PIN 8 to PIN 34 of Agnus. SOCKET 1, PIN 7 to PIN 42 of Agnus. SOCKET 1, PIN 15 to PIN 15 of Agnus. 8. Install the 7400 into socket 1, and the 7432 into socket 2. 9. Insulate the circuit board to prevent it from shorting on other components and mount it in a secure position. 10. Reassemble your Amiga just enough to test it. First test to ensure that 2MB of chip RAM is present. If so, reassemble your Amiga and insert the card into the video slot and check to make sure it works. If it does, then you are done and your Amiga will be as compatible as any A3000 or A2000 with a 2MB Agnus board installed. * R212 * <-This is the hole to insert the jumper wire. ------------------------------ |_ | _| GARY | | | ------------------------------ Diagram 1 Notch Notch -- --- ||--- _OE |--| D1 | | +V | | _CAS | | D3 | | D2 | | D3 | | D4 | | +V | | _WE | | D4 | | D1 | | D2 | | _RAS | | _CAS | | _WE | | _RAS | | A9 | | _OE | | A9 | | A0 | | A0 | | A8 | | A1 | | A2 | | A1 | | A7 | | A3 | | GND | | A2 | | A6 | | A4 | | A5 | | A3 | | A5 | | A6 | | A7 | | GND | | A4 | | A8 | | -- --------- 1MB x 4 ZIPP 1MB x 4 DIPP Top Views Diagram 2 To convert the ZIPP RAM to DIPP RAM, take a component carrier socket and mount the ZIPP RAM chip upside down on the component carrier. Use wire-wrap wire and wrap it to the ZIPP RAM lead and then wrap it on the correct pin of the component carrier socket. (Example: Wrap the wire on _OE of the ZIPP RAM chip and wrap the other end on the component carrier to match the DIPP RAM _OE. Keep in mind that if the ZIPP RAM chip is upside down, you will have to make a bottom view drawing of the ZIPP RAM chip by flip-flopping the lines in the top view shown above. There is a component carrier socket that doesn't have wire-wrap posts, but has solder posts. That type is fine, but you will have to solder the wire to the component carrier socket. Verify that they work by placing them in the sockets. If they are working fine, you can coat them with plastic-dip that is found in many hardware stores. Plastic-dip will harden to a nice insulated seal and will prevent the otherwise exposed leads from shorting out on anything that comes in contact with them. I used the ZIPP RAM since DIPP RAM at the time of hacking was about US $50 each. The ZIPP RAM was $18 each and the component carriers were $3 each. With a little work I saved US $29 per chip. I am not sure of the going rate of each type of RAM at this time. Document History: 1.0 - Initial Release 1.1 - Corrected wording and spelling. Added explanation on how to make DIPP RAM out of ZIPP RAM. 1.2 - Corrected wording and spelling. Added troubleshooting section. 1.3 - Added optional circuit instructions to make this hack work with video cards that output XCLK and _XCLKEN.