|1-How to convert a current ECS Amiga to



|1-the newer AGA chipset machines.



                        By C. Walker & J. Taylor


     Allows VGA, HiColor and HiRes modes on ECS machines (NTSC/PAL)

|1-PRELUDE.



        It  may have come to the attention of some of you that the newer
Advanced  Graphics  Architecture  (Hereon  refered  to AGA) chipsets are
little  more  than an improvement on the exisiting ECS chipsets that are
now  readily  available and are in current production machines.  We have
provided  this  data  to  enable  some  of  you to start developing your
software, as we have experienced various problems in producing the masks
required for the mass production of the newer chipsets.

|1-TECHNICAL.



        We  have  recieved many reports from our West German division of
the  successful  implementation of this minor modification.  Even though
it  is  a  minor modification we still recomend that you get a qualified
service technician to perform these modifications for you.

        The  current  8372A  and  8372B  (Agnus and Fat Agnus) have been
shown  to  be  able  to  support  upto  8Mb  of  chip  RAM through other
modifications.  It must be noted that in an any early model (pre rev 6a)
a500 motherboard, it is not possible to do this modification as the RAS*
and CAS* timings have a latency that is not acceptable in the addressing
of more than 1Mb of chip RAM.
^7^^460
        After  it  has  been ascertained as to wether
your system is capable of accepting the modification,
it  is  required  to  remove the cover as is shown on
your  users  manual (Appendix F).  After your case is
removed,  depending  on  your  particular system, you
will have to follow the in-step instructions for your
particular  machine.   Please  note  that  due to the
surface  mount  nature of the A600, this modification
is not possible.

|1-A500. (or A500 Plus in the UK.)



        After  the  top  cover  has  been  removed, the keyboard must be
unplugged  (take  note  of  the  orientation of the black cable, as this
connector is not keyed.) After successful removal of the keyboard, it is
neccesary to remove the RF sheilding.  Continued at MOTHERBOARD.

|1-A2000/A2500.



        With  the A2000/A2500 it is required that the four screws around
the  sides  of  the  case  and  the  one retaining screw at the mid-rear
section  of  the case be removed to enable the removal of the top cover.
After  the  casing  has been removed, it will be neccesary to disconnect
the  floppy  cables  and  the power supply from the motherboard.  Taking
note  of  the orientation of these cables, the removal of the drive bays
and  PSU  is performed by removing two screws from the front of the unit
and two more from behind the PSU itself.  Once completed, the drive bays
will simply lift out and expose the board and the 8372A/B.  Continued at
MOTHERBOARD.

|1-A3000.



        On  the A3000, the top cover must be removed, followed by any RF
type  shielding  (if  present) and then the floppy bays must be removed,
with  care  being  taken  on the position and orientation of connectors.
Once the floppy bays have been removed, the motherboard will be exposed.

|1-MOTHERBOARD.



        Once  the  motherboard  is exposed, it will be neccesary to find
and  identify  the  8372A/B  (Agnus/Fat Agnus) and to remove it from its
socket.   We  recomend  the  use  of  a PLC socket IC-extraction tool as
damage can easily arise.  Once removed, care must be taken once again to
ensure  the  correct  orientation  is  remembered  (This is quite easily
identifiable  by  a  white  marking  on  one  side  of the chip).  It is
neccesary to remove pin #36 from the 8372A/B.

        It  is imperative that the correct pin (#36) is removed, or your
Amiga will not function until you have replaced the 8372A/B!!!

        It  is now required to jumper a pin from the 8327A/B socket from
pin  #40  (*HSY)  of  the 8372A/B to pin #29 (*CCKQ) of the 8364 (Paula)
Sound and Peripheral controller.

        Once  this operation has been succesfully performed, all that is
required  is  for  the 8372A/B (Agnus) to be re-inserted into its socket
(Care  again  must  be  taken  to  ensure  that  the  chip  is correctly
orientated).

        Now  all that has to be done is the RF sheilding (if applicable)
has to be re-applied, then on the A500 series, the keyboard (again, take
care to ensure the correct orientation of keyboard connector).

        The  case must now be replaced, and if all has been completed in
good  order,  you  should now have an ECS machine that will give you the
higher resolution and color modes.

        Please  note:   This  does  NOT  increase the BUS width (It will
still  be  16  bits on A500/A2000 and full-32 bits on an A3000) nor will
the speed of the custom chips be increased.  This will only increase the
color  and resolution modes.  There is more documentation in the package
that will be supplied to you with your next notes.

        I hope that this document has been of some assistance to you who
have  been  asking  for  this modification, and I expressly hope that it
will  please  our  friends in the UK.  (Jez San, this is for you and the
Argonauts!)

                        By C. Walker & J. Taylor

End