System Booster/System Booster.iso/Archives/HardwareProjects/a500chip.lha/a500_1mb_chip_mod

Text File | 1993-09-13 | 8.1 KB | 176 lines

This is the CORRECT way to make your A501 chip ram!!

There have been other docs floating around saying to toggle the JP7A jumper,
but this is not true! Clear it instead! For all of you who have tried the
A501 chip ram fix and got nothing but a system crash on bootup, this is the
doc 4 u :-)

Thanks to Greg Change ([e-mail]) for information on how to
correctly do this :-)



     <<<DIRECTIONS ON HOW TO CONVERT YOUR A501 CARTRIDGE TO CHIP RAM>>>

DISCLAIMER: Attempting to conduct this procedure will by all means VOID YOUR
            WARRANTY! I shall not be held responsible for any problems due
            to this modification. I shall not be held responsible for any
            problems whatsoever.

Now I've got myself covered, lets' go on.

First off, it is required you have a revision 6A motherboard for this pro-
ject. It will work with others, but requires a 1mb Agnus chip and also re-
quires cutting a trace, which I am not familiar with at the moment.

If you are unfamiliar with electronic repair and modifications, ask an ex-
perienced technician to proceed with the modification.

READ THESE INSTRUCTIONS CAREFULLY AND THOROUGHLY BEFORE INITATING PROCEDURE!!

Tools needed:

  #10 Torx Screwdriver
  Flat Head Screwdriver
  Low Power Soldering Iron
  Razor Blade or Exacto-Knife
  Anti-Static Guard (optional)

1. Turn off computer and unplug ALL cords and peripherals from the computer.
   This includes the A501.

2. Now carefully flip the computer over. WARNING! Do NOT grab the A500 on
   the left side if the expansion dust cover is off! If you tug hard enough,
   you will snap off the connector, and the only way to replace that is by
   buying a new motherboard! It's just an edge-connector and can snap easily.

3. Plug in the soldering iron, just to get it all nice and warm. (make sure
   the iron has been on for at LEAST 15 minutes to avoid cold solder joints.

4. Now take the #10 Torx screwdriver and remove the 6 Torx screws around the
   edge of the case (at this point the bottom is facing up, of course. Do
   NOT remove any other screws on the bottom of your computer. Save the po-
   sition of each screw, because some may be intentionally different lengths

5. Flip the computer over again and carefully remove the top. If it doesn't
   remove with ease, use the flat head screwdriver to pry open the sides.
   Using a large screwdriver will make less pry marks in the case, or put a
   cloth around it or something. :-) Hopefully this won't permanently de-
   stroy the latches in the sides. They should just snap right back togethor

6. Now remove the cable going from the keyboard to the socket on the mother-
   board. It should just pull right out.

7. Now take the keyboard out and set it off to the side for now.

8. Now remove the two Torx screws on the left side of the computer facing
   the front. Remove the other two Torx screws holding down the grounding
   plate of the external expansion port. Now carefully remove these screws
   and the grounding plate. Remember the positions of each screw! Try not
   to mix them up! Also- Make note of the text under the disk drive. It
   should tell you the model, "B52/ROCK LOBSTER" (if you're lucky) and some
   other junk. Now look for the text "Rev. 6A". If your motherboard is not
   6A, like I mentioned before, you can still do the mod, but you need to
   cut a special trace and unfortunately, I cannot help you with this.

9. Now is the time to don your anti-static wrist strap, or whatever have
   you.

10. Look around the edge of the RF shield for small metal tabs holding the
    cover down. Now carefully bend these tabs up with the flat head screw-
    driver. Becareful not to bend them too much, or they will snap off.
    This is what happened to mine. :-)

11. Now remove the RF shield cover.

12. Get ready, here is the time to do the modification. Be careful not to
    hit the Amiga's plastic case with the soldering iron. I did this on some
    practice soldering equipment (broken VCR's etc) a while ago and once you
    destroy the case you're Amiga will no longer look pretty. (thank god I
    didn't do THIS :-)

Left|
Side|    *BE CAREFUL WHEN CUTTING - Be careful NOT to cut any other traces*
of  |
Ami |            Fig 1
   ++   ____
E  :: -|    |-
X  :: -|    |-
P  :: -| M  |- 1|       13. Now locate Jumper 2 (JP2) Between the CPU
A  :: -| C  |-  | JP2       and the ROM chip (just above and left of
N  :: -| 6  |- 2|   _       the ROM chip.) The jumper consists of three
S  :: -| 8  |-    =| |=     solder "pads". See how Fig 1 has these pads
I P:: -| 0  |- 3| =|R|=     numbered. When your computer arrived, pads
O O:: -| 0  |-    =|O|=     2 and 3 should have been set. We are about
N R:: -| 0  |-    =|M|=     to change this. Now take your razor blade
  T:: -|    |-    =| |=     or Xacto knife and just the trace between
   :: -|____|-    =|_|=     pad 2 and 3. Make sure, and check with a multi-
   ++                       meter or magnifying glass that there is no
                            connection between these two pads. Now take
                            your HOT soldering iron and solder, and
                            connect pads 2 and 1, just like the jumper
               =            depicted in Fig 1. Make sure it is a solid
               = Fig 2      connection and not a cold joint.
               =
               =
               =        14. Now it is time to locate the other jumper,
        JP7A   =            which is just left of the connector to the
               =            trapdoor (where the A501 goes). Search for
          1|   = Trapdoor   another three-padded jumper, labeled "JP7A"
               =            or JP7. Now cut the trace which was connecting
          2|   =            pads 2 and 3. Make sure it is a clean, solid
               =            cut. This jumper should be left open, and no
          3|   =            pad should be soldered to another.
               =
               =
               =

15. Now check and make sure all connections are firm and clean, and replace
    the RF cover. Then push down the metal tabs and make sure the cover is
    secure at those points.

16. Now replace the grounding plate and CAREFULLY screw the two Torx screws
    in. These are special screws- so as soon as it feels firm, no NOT turn
    ANY further! This can strip the screwholes and damage your case perm-
    enantly. Remember to put each screw in it's dedicated position.

17. Now replace the other two Torx screws and once again screw them in just
    until secure. Remember once again to put each screw in it's dedicated
    position.

18. Replace the keyboard and set it in the special slots so it is secure.
    Carefully replace the keyboard cord, and make SURE it is inserted the
    correct way. If it is not then I cannot guarantee your system will boot
    up and work correctly.

19. Now snap the top case of the A500 back on. Make sure it is perfectly
    aligned and all.

20. Now carefully flip over the A500, and remember not to grab the edge-
    connector! I have never seen this incedent happen but I'm sure it has.
    Such a simple mistake could cost you a whole new computer/motherboard.

21. Now insert each Torx screw. And once again remember to put each screw
    in it's dedicated position. (whew!)

22. Now return the A501 to the trapdoor, close it up and flip the Amiga
    over. (and now I KNOW you know not to grab the edge-connector :-)

23. Plug all other peripherals and cords back in, and turn the machine on.

24. If it boots up O.K, then hopefully you're in buisness. Now run a program
    like SysInfo or PerfMon to make sure you have 1024k of chip ram (1mb)

25. Have fun! It is now possible to load large large mods, have more graphic
    data in memory at once, play better demos, and, in short, fit along with
    the rest of the world! :-) Good luck!

*** If you are having any problems I encourage you to check all of these
    steps and make sure nothing was left out or improperly done.

    Stay Cool with your new 1mb of Chip Ram,

    Bill The Cat ([e-mail])
     (Will Jhun)