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THE OBESE AGNUS, THE NEW 500 BOARD AND OTHER RECENT EXPERIENCES

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�[33m
          THE OBESE AGNUS,THE NEW 500 BOARD AND OTHER RECENT EXPERIENCES.
          `````````````````````````````''''''''''''''''''''''''''''''''''
�[0m
    �[3m                        By Andrew Wilson  23/07/89.

  WARNING.. ANY MODIFICATIONS MENTIONED IN THIS ARTICLE SHOULD ONLY BE DONE
            BY TECHNICALLY COMPETENT PERSONNEL: TECHNICIANS ETC.(not
            engineers) AS REPAIRS TO THESE MACHINES ARE COSTLY AND SERIOUS
            DAMAGE EASILY DONE.THE REMOVAL OF PLCC CHIPS (A500 AGNUS) FROM
            THEIR SOCKETS WITHOUT THE PROPER TOOLS IS PARTICULARLY
            HAZARDOUS. MOST OF THESE MODIFICATIONS REQUIRE GOOD SOLDERING
            SKILLS ETC. ALL WORK SHOULD BE CARRIED OUT AT AN ANTISTATIC
            WORK STATION. STATIC DOES EXIST, IT IS NOT A FAIRY STORY PUT
            OUT BY 3M CORP. TO SELL THEIR ANTISTATIC GEAR.  SEE
            ANTISTATIC WARNING ELSEWHERE IN THIS SECTION. ALL POSSIBLE
            CARE HAS BEEN TAKEN IN PREPARING THESE NOTES BUT ANY
            MODIFICATIONS ARE DONE ENTIRELY AT YOUR OWN RISK.
            All modifications stated as fact have been done by me, mods
            put up as possibilities are my thoughts on a subject and have
            not been tried.
�[0m�[32m
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�[0m
      [Ed: Andrew is the brains behind the original Proton Ram boards,
           which are still valued very highly by their owners. He is now
           running his own Amiga-specific hardware manufacturing business
           (on a human scale, with human scale prices, too) and it may not
           be an exaggeration to say that there is little he doesn't know
           about the Amiga in general, and hardware specifically. He
           provides numerous products for all models of the Amiga,
           including 8-meg Ram boards, hard disks, digitisers, real-time
           clocks, and many other products. You'll see below that he
           really knows what he's talking about, and he's always been
           available to me when I have a hardware problem. He can be
           contacted at:

           2 Meredyth St,
           Millswood  5034.

           With the expert help of Mario Nicotra, this mod was done to my 
           early (Rev. 5A) A500, and it worked fine - the business of the
           switch from NTSC to PAL screens was done by bending the socket
           of pin 41 of the Agnes chip, perhaps the easiest of the alter-
           natives mentioned by Andrew. Note also that the full details
           required are here: all the docs from the US and even from 
           Commodore here tend to forget to show you how to make the change
           from NTSC to PAL...
�[32m
    |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||

                            IN THIS INSTALLMENT
                            ------------------

                 The Obese Agnus Chip

                 Obese Agnus Software Compatibility

                 Fitting the Obese Agnus to the REV5 A500 (Original 500)

                 The New REV6A A500 Board

                 The Different Types of A500s and Identifying Them

                 [ED: 2000 Modification follows at bottom] 
�[0m
�[33m
  The Obese Agnus Chip.
  ---------------------�[0m
   The Obese Agnus Chip (8372A or 318069-02) is the new Agnus chip capable
   of addressing 1 MegaByte of Chip Ram on the A500 or B2000. This allows
   you to have more than TWICE as many windows and screens open than is
   possible with a standard Fat Agnus equipped machine. If opening twice
   as many screens and windows isn't your thing then it also means that
   the Hi-res modes of such programs as Digiview, DeluxePaint and others
   which refuse to run until all extra drives, windows, screens are closed
   will now open and also allow you to run extra flip screens etc. Games
   such as Boulderdash/Emerald Mines which refuse to load unless all
   external drives are disconnected are now much happier as well.

    Commodore is now shipping the Obese Agnus in most of the current A500s
   (without telling anybody) although Commodore in the USA will admit to
   it when questioned. These A500s are set up in Fat Agnus Mode so that
   even if an A501 board is plugged into them no improvement is obtained
   without further internal modification.
�[33m
  Obese Agnus Software Compatibility.
  -----------------------------------�[0m
   Already 1 animation package (VideoFX 3D I believe) has been found which
   will not run with the 8372A in either Fat or Obese mode. This is a
   problem caused by the programmer reading or writing to registers in the
   Agnus chip in an illegal (non-Commodore approved) manner and may
   (should) be fixed in later releases of the package. CHECK that any
   software that you HAVE to use works with ONE Meg of Chip Ram before
   committing to this upgrade. All other programs tried so far, about
   150, have been completely compatible.
�[33m
  Fitting the Obese Agnus to Early A500s.(REV5 Boards)�[0m
  ---------------------------------------
   Contrary to a message appearing on many local Bulletin boards it is not
   necessary to have the new Rev 6A board to fit the Obese Agnus to an
   A500.  The 8372A can be fitted to the older Rev 5 boards simply by
   doing the following :

   1 Remove the Fat Agnus 8371 from its socket (see warning above).
     Check orientation of pin 1 to facilitate installation of 8372A. Pin
     41 of the Agnus socket which is earthed on all REV5 boards controls
     whether the A500 starts up in NTSC or PAL mode. When it is earthed
     the Obese Agnus initialises in NTSC Mode which means that all USA
     owners need to do is plug in the chip and they are in the correct
     mode. We on the other hand have to de-solder and remove the socket
     from the board to isolate pin 41 which is connected to earth on both
     sides of the board. This chip was designed in the USA!! Removing
     the socket is a difficult and laborious task so other methods of
     isolating pin 41 are possible. I DO NOT recommend trying to drill
     through the board as the two pins 41 and 42 are very close together,
     the trace between them is thick and there are thin tracks either side
     of it under the socket on the top of the board. Bending the contact
     on the socket is a possibility but make sure you get it right or
     you'll be removing the socket anyway. Placing a thin piece of hard
     plastic, eg mylar, between the pin and the contact is another
     possibility. By putting a SPST toggleswitch between pin 41 and earth
     it is possible to switch between NTSC and PAL on resetting the
     machine. This would give good compatibility with American software
     and for this reason and others DO NOT just break or cut pin 41 off
     the chip. Pin 41 is taken to a jumper pad on REV6A boards.


                1 1                   8 8 8 8 8 7 7 7 7 7
                1 0 9 8 7 6 5 4 3 2 1 4 3 2 1 0 9 8 7 6 5
 BEVELED CORNER | | | | | | | | | | | | | | | | | | | | |
              /ЇЇЇЇЇЇЇЇЇЇЇЇЇЇЇЇЇЇЇЇЇЇЇЇЇЇЇЇЇЇЇЇЇЇЇЇЇЇЇЇЇЇЇ|
         12 -|                      ¤                     |- 74
         13 -|                      ^                     |- 73
         14 -|                      |                     |- 72
         15 -|                INDENT FOR PIN 1            |- 71
         16 -|                                            |- 70
         17 -|                                            |- 69
         18 -|                                            |- 68
         19 -|                                            |- 67
         20 -|                8372A                       |- 66
         21 -|                                            |- 65
         22 -|                                            |- 64
         23 -|            TOP VIEW                        |- 63
         24 -|                                            |- 62
         25 -|                                            |- 61
         26 -|                                            |- 60
         27 -|                                            |- 59
         28 -|                                            |- 58
         29 -|                                            |- 57
         30 -|                                            |- 56
         31 -|                                            |- 55
         32 -|                                            |- 54
             |____________________________________________|
                | | | | | | | | | | | | | | | | | | | | |
                3 3 3 3 3 3 3 4 4 4 4 4 4 4 4 4 4 5 5 5 5
                3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3


  2  Insert the Obese Agnus 8372A into the socket paying particular
     attention to the orientation. Pin #1 is located in the centre of the
     side immediately clockwise from the beveled corner of the chip and is
     marked by a small dimple. The 8372A should be installed with pin 1
     to the front of the socket. This is marked by a large 1 on the
     silkscreening on the circuit board just above the words "FAT AGNUS".
     I overstress this point because this is an expensive chip and a
     wrongly inserted chip which has had power applied to it probably has
     a value of 0000 dollars. The socket on the REV6A boards has been
     rotated 90 degrees anticlockwise. BE WARNED!!

  3  Locate the jumper JP2 on the circuit board to the right of the 68000
     chip.  Cut the trace between the centre and lower pads carefully with
     a sharp knife. Join the centre and upper pads with a small piece of
     light wire.  This jumper changes the address of the A501 board or
     equivalent from C00000H to 080000H to make it contiguous with the
     first 512K of memory to give a 1MEG block of chip ram. The three
     pads of JP2 can be wired to a SPDT toggleswitch to allow changing
     from one memory location to the other if there is any software
     incompatibility with the new setup.

  4  Pin 32 of the GARY chip (located above right of the Agnus socket)
     must be open circuit for this upgrade to work. This pin is the
     *EXRAM signal which is normally earthed by the A501 board when it is
     plugged into the A500. Several methods of achieving this are
     available as follows:

       a. If you have installed one of my A501 memory disable switches
          or other similar modification which open circuits pin 32 of the
          A501 memory expansion connector then this will serve the
          purpose. Leave it in the OFF position and disregard the rest of
          section 4.

       b. Locate the GARY chip and remove from its socket. Locate pin 32
          and CAREFULLY bend it slightly outwards so that when GARY is put
          back in its socket pin 32 does not go into its socket. Return
          the GARY chip to the socket making sure that it is correctly
          positioned ie. pin 1 and notch to the right hand side. Pin 32
          can be connected through a SPST toggleswitch to earth to
          preserve compatability with the Fat Agnus.

                          Notch in end of chip
                                  |
                                  V
                         _________________
   Pin numbers >     1 -| o     \_/       |- 48
                     2 -|                 |- 47
                     3 -|                 |- 46
                     4 -|                 |- 45
                     5 -|                 |- 44
                     6 -|                 |- 43
                     7 -|                 |- 42
                     8 -|                 |- 41
                     9 -|                 |- 40
                    10 -|                 |- 39
                    11 -|                 |- 38
                    12 -|                 |- 37
                    13 -|                 |- 36
                    14 -|     GARY        |- 35
                    15 -|                 |- 34
                    16 -|      5719       |- 33
                    17 -|                 |- 32     <  Pin to be bent in 4b.
                    18 -|                 |- 31
                    19 -|                 |- 30
                    20 -|                 |- 29
                    21 -|                 |- 28
                    22 -|                 |- 27
                    23 -|                 |- 26
                    24 -|                 |- 25
                         -----------------

     *******   ALL DUAL INLINE PACKAGE INTEGRATED CIRCUITS ARE NUMBERED IN
               THE SAME MANNER, ONLY THE NUMBER OF PINS VARIES.

  5  Check all work done in all previous stages, and if everything is
     correct connect it to power supply, mouse and monitor and turn on the
     power. If it does not boot up as normal power off immediately and
     recheck. The longer the power is switched on with a fault the
     greater the damage. Check for bent or folded pins on GARY if you
     have had him out. If you have the disk drive disconnected or wrongly
     connected it will take a lot longer before the hand and disk appear
     on the screen.

  6  Once you have booted successfully run PERFMON from the TOOLS drawer
     of the EXTRAS Disk [Ed: or PopInfo from MD11]. It should show 1MEG
     of Chip Ram and no Fast Ram on a 1MEG A500. Now try loading a
     picture, The Tiger on Megadisc 5 is most suitable, repeatedly. It
     should be possible to load more than twice as many as before (about 8
     as against 3 I think from memory).


�[33m
  The NEW REV6A 500 Board.
  ------------------------�[0m
   This board has been shipped by Commodore for approx. 2 to 3 months.
   The main reason for the change has been to allow Commodore to use the
   newer 1 Megabit chips and to allow for 1 megabyte of memory on the main
   board. This means that the A501 board is no longer needed if the extra
   512K is installed on the main board. Current cost of this upgrade is
   approximately $160.00 . If the Real Time Clock is needed then clock
   boards plugging into the A501 slot are available for $50-60. There is
   provision for several resistor packs on the board although they are not
   fitted and their use is not clear. The change has little to do with
   the Obese Agnus upgrade although it is a little easier to fit to a
   REV6A board. The board also contains several new jumper pads, details
   of which are given below.

             REV5 BOARD    REV6A BOARD     APPARENT USE

   JP1        Yes          Yes    Connects 555 reset timer to main reset

   JP2        yes          yes    Maps A501 @ C00000 or 080000

   JP3        yes          yes    Swaps *CAS of 512k banks of RAM

   JP4        no           yes    PAL or NTSC via pin 41 of Obese AGNUS

   JP5        no           yes    28MHz CLK, XCLK and XCLKEN to AGNUS

   JP6        no           yes    7MHz clock on pin 7 of 86way Exp Connector

   JP7A       no           yes    Controls *EXRAM to GARY

   JP7B       no           yes    CIA TICK from VSYNC or pin 32 of A501

   JP8        no           yes    LPEN from FIRE0 or FIRE1

   JP9        no           no?

   J910A      no           yes    Connects AUDIN to pin 18 of RS232 Port

   JP10B      no           yes    Connects AUDOUT to pin 11 of RS232 Port

   JP11       no           yes    Connects CSYNC to BCSYNC or Video Hybrid

  (A Week Later)
   As can be seen from the above table most of these new jumpers are for
   convenience and do not represent radical improvements over the previous
   board.


    Conversion of a REV6A board to work with Obese Agnus is fairly simply
   and will be covered in a later article which will also cover fitting
   the extra 512K of RAM to the main board.

�[33m
 The Different Types of A500s and Identifying Them.
 ---------------------------------------------------�[0m

    This section does not attempt to identify the different types of disk
   drives, keyboards etc. which, particularly in the case of the A500,
   seem to change almost weekly.

  The A500.
           The base model of the range which, contrary to what B2000
           salesman say, is expandable to Approx. 15 Meg of RAM, Hard
           Drives, etc.  Somewhat limited power supply so a larger one is
           needed for hard drives.

   There are two basic types :

        A. The original REV5 board supplied from the beginning up until
           early 1989. Requires the A501 Board or equivalent for
           expansion to 1 Meg and use of Obese Agnus.

        B. The new REV6A board supplied from April/May 1989 on. The way to
           recognise it is to check the expansion bus connector on the
           left hand side of the computer. You'll notice that the early
           model A500 has a "fat finger" metal strip at the back end of
           the connector - the new A500 doesn't, instead it has two thin
           "fingers", ie, 2 metal strips in the corresponding place, of
           the same width as the rest of the strips of the connector.


    More on this and other related matters in the next issue.


    2000 MODIFICATION

    Ed: The modification for the A2000 is pretty similar, and has been 
    done by Mario (mentioned above) on a very souped-up system. Keeping
    in mind all the warnings and hints above, it goes like this:

    A. Remove computer cover, floppy cable (noting position of the red
       wire on the cable), power plug from connectror CN400, and power
       supply and drive assembly from the main unit.

    B. Remove the old slimmer Agnes as above, preferably using a chip
       extractor. Insert the new chip with the right alignment.

    C. Find Jumper J101 located on the lower right side of the power 
       connector CN400, and consists of 3 posts - 2 of the posts are 
       shorted together using a shorting block. Remove the shorting block
       and move it to the left, towards the power connector. For further
       info, see Page 13 of the A2000 system schematics - this jumper
       will enable address line 19 from the 68000 which controls the 1 
       meg address range.

    D. Locate and cut Jumper pad J500 (to the lower left of the 8520 at
       U301). This is a 2-pad jumper with a trace connecting the two 
       pads. See Page 9 of the A2000 system schematics - cutting this
       trace keeps the _EXRAM signal from being tied to ground.

    E. Finally, to enable PAL rather than NTSC - locate and cut J102, 
       NOT J201 as suggested in some docs. This is the equivalent of 
       bending pin 41 of Agnes in the A500 mod.


       The mod is now finished, so re-assemble the unit, power up and
       hope for the best! And don't attempt it unless, as mentioned 
       above, you're very adept at electronics hacking. Show these docs
       to such a person, however, and there should be little difficulty.
 


�[32m
    |||||||||||||||||||||||||| END OF ONE_MEG_AGNES ||||||||||||||||||||
�[0m



                   �[43m�[32m SAVING DF0: - BOOT UP FROM DF1: �[0m

                                                  by�[3m Les Ayling�[0m

�[32m
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�[0m
    Several of my friends who are Amiga owners have had problems with the
   internal drive. This modification will overcome that problem by
   allowing Amiga 500 owners to boot from df1:.

    This mod is also useful for people who own the Commodore 5 1/4 inch
   drives and wish to boot from them. More importantly, people who have
   added an 80trk 5 1/4 inch drive (such as myself) as described in the
   file ADD_5.25_DRIVE can boot from it. As 5 1/4 inch disks can be
   bought for as low as $5.95 for 10 in some places, it is well worth
   considering as a cheap backup library option OR indeed as an
   alternative primary storage medium.

      You will need the following tools and parts:

      * Low wattage soldering iron, suitable for PCB's
      * DPDT switch mini toggle variety is fine
      * 1 foot of ribbon cable
      * solder
      * small snippers
      * hand drill
      * tool to unscrew the @#$%^& non-standard case screws
      * Exacto knife or similar

    Start by unscrewing the 6 hex style screws around the edge of the
   case (Goodbye warranty!).  Do not remove the three phillips screws as
   they are holding the drive in place.  Turn the machine back the right
   way up and remove the lid by pressing around the edge to ease off the
   catches.  Remove the keyboard making careful note of the orientation of
   the connector on the main board!!!!!  Now remove the further 4 hex
   screws which are holding the top rf shield in place and remove the
   shield.  Unplug the disk drive POWER cable from the drive end only.

    Remove the 34-way disk drive patch lead taking note of its orientation
   (This saves so much time when you have forgotten later on!)  Unscrew
   the Disk drive unit and remove it.

    The main PC board should now come free with the lower RF shield.
   Unscrew the hexagonal socket retainers on the I/O connectors at the
   rear of the board and this shield should come free.

    You are now ready to start!

    Locate connector 11 (CN11) on the component side, this is the socket
   that you just unplugged the disk drive patch lead from.  In front of it
   should be U8 which is an 8520 chip.

    CN11 is 2 rows of 34 pins.Count along the front row from the right
   hand side until you see the 5th and 6th pins (pins 9 and 11 of the
   connector respectively).  There should be two circuit traces that lead
   from these pins and disappear under U8.  Using the exacto knife cut
   both of these traces leaving no stray copper. A 1mm cut should be
   sufficient.

    Turn the board over to the solder side.
    Leave the board for a moment and get the DPDT switch.
    For ease I will label its pins as such:

        A   B

        C   D

        E   F

    Cut a piece of ribbon cable about 1' long with 4 conductors.
    Strip and tin the wires then connect them to A, B, C and D.
    Cut two small pieces of wire and connect A-F and E-B.

    Tin and strip the other ends of the ribbon cable.Using the snippers
   trim these tinned ends until there is about 1 1/2 to 2mm showing. Any
   longer is unnecessary and can lead to solder blobs etc.

    Grab the Amiga pc board again. On the solder side locate pins 9 and
   11 of CN11 as described earlier. Solder the lead from A to pin 9 and
   the lead from B to pin 11.

    Locate pins 13 and 14 of U8.

    If you are unsure of pin numbering on IC's refer to one of the data
   sections of DSE's or ROD Irving catalogues.  Otherwise looking at the
   chip there is a notch at the right hand end of the board. Pin 1 is
   behind this notch (relative to the pc board) and the numbers increase
   in an anti-clockwise fashion around the chip.  Solder the lead from C
   to pin 13 of U8 and the lead from D to pin 14 of U8.  That completes
   the soldering side of things.

    All that remains is to drill a hole for the switch and put the rest
   back together. There is a convenient spot to the right of the joystick
   socket that will house 3 or 4 switches comfortably.

    PLEASE PLEASE PLEASE be careful of the orientation of the connectors
   when assembling your amiga.

    To use the mod:
             1. Remove ALL disks from ALL drives.
             2. Flick the switch to the NORMAL position.
             3. Turn the machine ON or reset if already ON.
             4. If you wish to boot from drive DF1: now is the time to
                flick the switch to the NON-standard position.
             5. Insert the appropriate disks in the appropriate drives.

    HOW it works.
   The mod works by switching the drive select lines SEL_0 and SEL_1.
   SIMPLE!
�[33m
    IMPORTANT:!!�[0m
   The switch must be in the NORMAL position when you either turn the
   machine on or reset.The reason for this is that after a cold or warm
   boot the KERNEL roms go looking for what equipment is connected to the
   system. A part of the GARY chip which is triggered by the SEL_0 signal
   provides seperate MOTOR_ON signals for the internal and external
   drives. When the switch is in the ALTERED position the GARY chip is
   fed by the SEL_1 signal and surprise surprise! the KERNEL roms won't
   find the internal drive!  However is is PERFECTLY safe to change the
   switch at ANY time the power is on (without disks in the drives!). So
   if the switch is changed after the roms have found what drives are
   online, the drives 0 and 1 will operate fine only reversed.  More
   circuitry could have been added to swap the motor_on signals so that
   this extra switching wasn't required, however most people would
   probably like to keep their mods to the main pcb to a MINIMUM!
�[33m
    *NOTE*�[0m
   If the switch is changed while disks are inserted in the drives,
   AmigaDOS will become confused as to what volumes are on line and if
   your write-protect tags are OFF, chances are your directories will be
   CLOBBERED!!

    The mod is relatively simple, however if you are unsure of your
   ability to perform it.. DON'T. get some hardware oriented person to
   help or drop me a line at PARAGON bbs if in Sydney, or via Megadisc and
   I may be able to help or do it for you at a small nominal cost.
   Naturally I cannot guarantee your labour content so therefore I cannot
   make any warranties, implied or otherwise, as to the suitability or
   performance of this modification.  However I can say that I am not too
   worried about my software collection as I have a set of bootable 5 1/4"
   backups!!

    Good luck and I hope that this is of some help.

�[32m
    ||||||||||||||||||||||| END OF BOOT_FROM_DF1 ||||||||||||||||||||||||
�[0m



			AUDIO BOOST ON THE AMIGA 500
----------------------------------------------------------------------------
This hardware hack is not advanced and gives you a much higher volume out
of your Amiga (With good quality!)

First remove the screws (This will destroy your warrenty!) from the Amiga
shell (even the screws for the drive!) now carefully open your Amiga,
There are some pigs holding the shell at it's place so don't break those!
(as i have!)   Now remove the screws from the metallic shield and gently
remove the keyboard cable! (Remember the direction the connector are!)
now remove the drive! (Yet another time remember how it was connected!)
now find the filter (LF347) near this circuit you find the condensators
at 22uF (you will actually find two!) the condensators are named C334 and
C324 and two resitors named R334 and R324 now take a dual switch and connect
it like this:

		SWITCH:

    +------------1  4------+
    |                      |
    | +----------2  5----+ |
    | |                  | |
    | |          3  6    | |
    | |                  | |
    | |                  | |
    | + +C334            | + +C324
    +--  R334            |
			 + R324

And now you can boost more sound of ya Amiga, but be carefull you can
destroy
your speekers if ya pump up the volume too much!
(The level meter on my gettoblaster goes to max if i turn on my boost)

I must say that if your Amiga brakes down cause of this little hardware hack
then don't blame me!

And if you are not good at soldering then let someone else do it! (even if
the soldering on this hack is really easy!) and DON'T USE A HIGH WATTAGE
SOLDER IRON! (MAX 25 WATT)

Chucky of Sargon
			    PAUSE ON THE 68000
-------------------------------------------------------------------------
This hack works on all computers with a Motorola 68000 processor!
(Amiga, Mac, Atari)   Well i will describe it as it's on the Amiga!

First remove the shell! (Ya warrenty will go to hell) find the processor
(On the Amiga 500 it's located at the left side, On the 1000 it's on the
right side, I don't know where it's on the 2000!) solder a wire on pin 17

	  
	The notch means that the pin 1 is on this side
	(start to count from the little dot!)

	   +--_--+ 
	1 -|.    |-64
	2 -|     |-63
        3 -|  M  |-62
        4 -|  O  |-61
        5 -|  T  |-60
        6 -|  O  |-59
        7 -|  R  |-58
        8 -|  O  |-57
        9 -|  L  |-56
	10-|  A  |-55
	11-|     |-54
	12-|  6  |-53
	13-|  8  |-52
	14-|  0  |-51
	15-|  0  |-50
	16-|  0  |-49
   +--- 17-|     |-48
   |
   |	    ETC.
   |
   |
   |	SWITCH:
   |
   +-------1

	   2-------- TO GROUND (THE METALLIC SHELL IS A GOOD GROUND)

	   3



Thats it!   It's not dangerous to pause the computer as some guys thinks
Even if it can look strange sometimes (even crash sometimes) but that
depends how the programmer have done some things! (like showing bitmaps
and so on!)

The DMA is not stopped with this pause so for example sounds and copperlist
will go on on the Amiga (not musics like soundtracker then just the sounds
will go on but no new will come cause it's a little program but the
processor is halted so no new data will come!)

This feature can be good if you reads for example a scrolltext and the
phone is ringing then you just have to pause or if you want to check
how some guys have made some effects in a proggy

If you are not good at soldering let someone who is good to solder in your
computer!

AND DON'T USE A SOLDER IRON WITH A HIGHER WATTAGE OF 25 WATT!!!

Chucky of Sargon



                 �[42m�[33m HOOKING A 5.25" DRIVE TO YOUR AMIGA �[0m

                                               by�[3m Les Ayling�[0m
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    Hooking up a standard 80 track, double-sided, 5 1/4" floppy disk drive
   as drive df2: or df3:

    Looking at the connector from the back side of the external drive, the
   pin out is as follows:


            712  11  10  9   8   7   6   5   4   3   2   1


                 23  22  21 20  19  18  17  16  15  14  13


    34 Pin edge connector pin-out is as follows:


             34 32 30 28 26 24 22 20 18 16 14 12 10  8  6  4  2


             33 31 29 27 25 23 21 19 17 15 13 11  9  7  5  3  1



    Wire a DB25 (RS-232) connector with pins 13 and 25 cut off per the
   following configuration:


              34 Pin     23 Pin

              -----------------

              34 ---------  1

              32 --------- 13

              30 ---------  2

              28 --------- 14

              26 --------- 15

              24 ---7---- 16

              22 --------- 17

              20 --------- 18

              18 --------- 19

              16 ---------

              14 ---------  9

              12 --------- 21

              10 -- tie to ground, keep the motor running all the time

               8 --------- 22

               6 --------- 20

               4 ---------

               2 ---------

   all odd numbered pins of the 34 pin connector should be tied to pins
   3, 4, 5, 6 & 7 of the 23 Pin connector (grounds).


    In addition, pin 11 of the 23 pin connector should be wired to a
   momentary push-button that can be activated whenever a diskette is
   removed and replaced with another.  This tells the DOS that a different
   diskette has been inserted into the drive.  Simply change the diskette,
   push the button and hold until DOS accesses the drives.  The switch may
   then be released.  This function is necessary due to the fact that the
   DOS seems to read the directory of the current diskette into ram, and
   unless the DOS is told of another diskette being used, it will either
   ask you to replace the diskette that was in the drive or write to the
   diskette using parameters from the previous disk.  This, of course, is
   very undesirable.


    Also, note that the drive must be connected when booting DOS or it
   will not be noted as being on-line.  The diskette does not have to be
   inserted, just the drive plugged in.


    Do not make any connections to the 23 pin connector, pins 23 or pin
   12.  These pins provide power to the Amiga drive 1 and may not be used
   to power an external 5 1/4" drive.  An external power supply must be
   used.


    The 5 1/4" drive selection header may be programmed as drive for drive
   2.  Drive 1 selects as DF2: and drive 2 selects as DF3:.


    A motor on latch circuit may be built to eliminate the motor
   continuously turning, however, the way indicated above is the quickest
   and simplest method to get another drive on-line.


    After this procedure is completed, the 5 1/4" drive may be used just
   as any normal Amiga drive.


    Considering the $295.00 list price of the Amiga drives, versus about
   $50 dollar price of 5 1/4" drives, it's a real bargain.


    *** As always, with any hardware project -
    (1) - if you are not sure of what I am talking about, get
   knowledgeable help and
    (2) - TRIPLE CHECK your work before plugging in the new drive.


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