Floppyshop 2/Floppyshop - 2.zip/Floppyshop - 2.iso/diskmags/0022-3.564/dmg-3413/news.txt/blitter.asc

Text File | 1989-04-05 | 15KB | 313 lines

                  ######################################
                  #                                    #
                  #          Blitter Upgrade           #
                  #                                    #
                  # for Not-so-Blitter-ready 1040 ST's #
                  #                                    #
                  #         by Erik Muldowney          #
                  #     (sent in by Rab Gilmour)       #
                  #                                    #
                  ######################################


I bought my 1040ST about 2 years ago. When the first one arrived it didn't
work (the power supply made a sizzling sound),  so I sent it back. The one
I  got  back is a Revision B.  Little did I know just how  troubling  this
motherboard configuration would be.  This is the one that has a spot for a
Blitter, but no corresponding solder pads. Also, the RAM chips are located
under  the power supply,  which made upgrading to 2.5 Meg a real  headache
(read on).   I couldn't use Barry Orlando's procedure, but had to do it by
the  seat of my pants (but that's another story).

One  day I was reading one of the online ST magazines.  I came across   an
article  by  W.K.  Whitton  which  spoke  of  FaST  Technologies  products
including a Blitter upgrade board. It stated that if your ST already had a
spot for a Blitter you didn't need a board.  All you had to do was install
a socket and a Blitter and remove two blobs of solder and away you went.

So I had a look inside my ST and sure enough,  there was a square  pattern
of 64 holes shaped just like GLUE and MMU. I saw several  solder pads with
blobs on some of them too,  so I ordered my chip and socket that very same
day.

But  I hadn't looked close enough.  Those solder blobs were not  for   the
Blitter, but for the ROM chips (2 or 6 chip set selectors).

So as you might expect my Blitter didn't work when I installed it,  indeed
it crashed the computer entirely.  Apparently,  when this motherboard  was
designed the Blitter was still on the drawing board.  Several  connections
were wrong with or without solder  pads and several other little things.

It  took  me  nearly two months to figure  it  out.  I  corresponded  with
W.K.Whitton on Genie, as well as Jim Allen of Fast Technolo- gies. I tried
to  get a Technician at an Atari dealer in Orlando  to let me have a  look
at his schematics,  but "Atari prohibits us from doing that".   Instead he
gave  me  an incomplete hand-drawn schematic of some  of  the  connections
between  the chips (it wasn't enough).  I called  up Atari and asked  them
for help (what a joke).  I got bits and pieces of information from all  of
them  (well,except  Atari),  but  nobody gave me  the  entire  picture.  I
finally ended up having to  ask a friend with a more recent version of the
motherboard to let me poke around inside with an Ohm meter. Still,you have
to know  what you're looking for, so that took several tries. But I got it
in the end.

So now,  in hopes that I might save somebody else out there the  headaches
I went through,  I'm writing this procedure. My original  intention was to
save the 50 bucks a board would cost. I don't know if it was worth it, but
I'll  say it was since I'm a computer  Engineering major and I  learned  a
heck of a lot about the guts of an ST.

First,  I'll  start by giving the usual warnings and disclaimers  seen  in
most do-it-yourself hardware hacks:

WARNINGS AND DISCLAIMER
-----------------------

   1)  Doing this will most certainly void your warranty.  But  if  you
   have  a revision B motherboard your warranty is probably history  in
   any case.

   2)  The  author  makes no guarantees that this  will  work  on  your
   machine  and accepts no responsibility for things you might  fry  in
   the process.

   3) If you are a novice at this sort of thing,  and doing things like
   cutting traces scares you,  pay someone else to do it so he can  buy
   you a new one if he botches it.  Next,  I think a list of things you
   will need is in order:



WHAT YOU WILL NEED
------------------

   1) TOS 1.4 - what good is having a Blitter if you can't use it?

   2) Blitter chip and socket - you can get these from Toad  Computers
      I think  (301-544-6943), I got mine at Midtown TV in  Ohio.
      Shop around and don't pay more than $80 for the lot.

   3) A 4700 ohm, 1/4 watt resistor - that's yellow-violet-red

   4) jumper wire - I bought a spool of wire wrap at Radio  Shack.  Its
      a real pain to strip the ends without one of those tools, but I'm
      on a budget.

   5) 15W grounded soldering iron - in other words make sure the  plug
      has  three prongs or you're asking for trouble in  the  form  of
      static discharge.

   6) Solder sucker bulb - I was too cheap to spring for a  desoldering
      iron,  but I paid for that mistake when I did that memory upgrade
      and had to take out 16 RAM chips.  But since there is only solder
      in the holes where the Blitter socket goes,a bulb works fine.

   7) Ohm meter - I used an LCD Digital multimeter which  hardly  uses
      any current at all.

   8) Real sharp exacto knife

   9) Solder, screwdrivers, magnifier,

  10) Reference  material - I had an Abacus ST Internals Rev.3  and  a
      Sam's  Computerfacts for the 520ST on  hand.  Believe  me,  they
      proved invaluable. And now for the procedure:


STARTING WORK
-------------

    Step 1) Set up your desk - clear all that junk off, make sure it is
    ======= free of dust,well lit and has plugs available.  now lay out
    a   towel  (not one that is prone to static cling) and a  sheet  of
    aluminum foil.  Ground it and yourself.  I took my metal wristwatch
    and put it on my ankle and aligator  clipped it to a ground source.
    A  static mat would be nice too.   There's probably no end  to  the
    precautions a static paranoid can  take.......

    Step 2) Disassemble your ST to where you can take your  motherboard
    ======= and place it by itself on the foil.You should take all  the
    screws  put them in a jar or else they'll fall into the shag carpet
    and  disappear  into hyperspace or the universe where one  of  each
    pair  of socks goes (I think my dryer is the gate).

    Step 3) Use the soldering iron in one hand to heat up  the  wave-
    =======  soldered  holes  and suck them out with the  bulb  in  the
    other. I suggest you alternate around the pattern so as not to heat
    up  one spot on the board too long.  It may take several tries  per
    hole  before  you get the hang of it (I never said  this  would  be
    fun).

    Step 4)  Insert  socket. STOP!!!  make sure  you  have  it  aligned
    =======  properly.  On my board there was an outline,  as  well  as
    numbers  by the corners.

    You  might want to take an Ohm meter and make sure that   pin 5  is
    ground, pin 1 is 5V, etc. just because it would be a real nightmare
    to  have  to take this one out again.

    Did you put it in wrong?  That'll teach you to skip ahead.  Well if
    you did I wouldn't suggest filing the corner off your Blitter chip.
    You might be able to use a small drill on the socket to carve out a
    corner though...

    Step 5)  Don't put the Blitter in just yet.  That's just  one  more
    =======  thing to   get zapped.  Now we're going to do  some  trace
    cutting. Won't this   be fun?

    Cut the following traces:

    A)  On my ST pin 45 of the GLUE goes to pin 28 of  the  Blitter.  I
    have  no  idea  why they did this because pin 45  of  GLUE  is  not
    supposed  to  go anywhare.  Cut the trace right  where  it  touches
    GLUE's pin 45.

    B) On my ST pin 27 of GLUE is connected to pin 11 of the CPU.   The
    Blitter  is going to intercept this one,  so cut the trace    right
    where it touches GLUE's pin 27.

    C) Now here's where it get's a little tricky.  On my  machine,  pin
    12  of the CPU was connected to pin 41 of GLUE -AND- to pin 29   of
    the Blitter.  The Blitter pin is right, which saves you a   jumper,
    but the GLUE has to be disconnected from them.  Follow   the  trace
    out from GLUE's pin 41. Somewhere it should branch  out into a "T",
    going off in two directions. If so, cut the   trace just before the
    "T".  This way pin 12 of the CPU and pin   29 of Blitter are  still
    connected together (use an Ohm meter   to make sure) but GLUE's pin
    41 is not connected to either of   them.


    Another possibility is that the trace from GLUE's pin 41 just  goes
    straight to the Blitter pin 29 but then keeps going to the CPU  12.
    If  this is the case,  cut the trace just before   it  touches  the
    Blitter pin 29. That way you'll leave some   thru-holes in the path
    still  connected to GLUE's 41.  You'll   see why this is  important
    later.  If  any of this is confusing to you,  check the  schematics
    I've included.

    Well, if your board is just like mine, that should be all the trace
    cutting you have to do. Now for the jumpers.

    Step 6) These  jumpers  are going to be on  the  underside  of  the
    ======= board, so you want to cut them to only slightly longer than
    the  minimum   length,  and  you  want to  strip  off  only  enough
    insulation to wrap around a pin.  My exacto knife has a pin on  the
    other  end,  so get something like this to wrap around so  you  can
    bend a little loop in the end of each jumper.

    Install the following jumpers:

    A)  Pin 27 of GLUE to pin 37 of the Blitter - on my machine pin  37
    of  the Blitter went nowhere,  and so does pin 27 of GLUE now  that
    you've cut its trace, so just do this one pin to   pin.

    B)  Pin  28  of Blitter to pin 11 of CPU - you should  be  able  to
    attach this jumper to thru-holes instead of pins.  Leave the   ends
    of the jumper straight.  If you'll remember,  pin 28 of the Blitter
    used  to  be connected to GLUE's 45 until you  cut  the  trace,  so
    follow  the  trace out from GLUE's 45 until you get  to  the  first
    thru-hole past the cut you made.  Now test it with an Ohm meter  to
    make sure it is indeed connected to Blitter pin 28, and if so, heat
    the thru hole and stick one end of the jumper in it.

    Next,  follow  the  trace  out  from GLUE  27  (which  used  to  be
    connected  to  CPU  pin 11) until you get to  the  first  thru-hole
    past  the  cut,  and test it with an Ohm meter to make sure  it  is
    connected  to  CPU pin 11.  If it is,  stick the other end  of  the
    jumper in there.

    C)  Pin  41 of GLUE to pin 40 of Blitter - since Blitter's  pin  40
    goes  nowhere you'll have to solder one end of the jumper  directly
    to  it.  And  since  you  are going to need  a  thru-hole  that  is
    connected to GLUE's pin 41 you'll have to do the same there.

    Step  7) The Resistor - this is one of the parts I that  eluded  me
    for so long. Some of these signals are made high by connecting them
    to +5VDC via a resistor.  Most of the resistors are already  there,
    in  a resistor pack near the CPU.  But one of them isn't,  and  its
    enough to make the system fail.

    So  what  you  are  basically about to do is  connect  a  4700  Ohm
    resistor  between  +5V and the GLUE's pin 41 to  Blitter's  pin  40
    connection  (now you know what the thru-hole is  for).  Follow  the
    trace out from GLUE's pin 41 until you get to the first  thru-hole.

    Remember  where it is so you can find it on the top of  the  board.
    Now turn the board right side up and locate the hole again.  Use an
    ohm  meter  to verify that it is the right one (you can  touch  the
    other  probe to pin 40 of the Blitter socket if you don't  want  to
    touch GLUE).

    Now install one end of the resistor in this hole, all the way in so
    the resistor package touches the board and most of the wire  sticks
    out the bottom.  Cut off the extra.

    Now look around the top of the board on the lower right corner  for
    two resistor set in the board.  What you are going to have to do is
    locate  a +5VDC source by using the ohm meter.  Touch one probe  to
    pin 1 of the Blitter socket,  and touch the other to either end  of
    those resistors in the corner.  When you get 0 Ohms,  you've  found
    it.

    This is where one end of your last jumper goes,  and the other  end
    connects to the new resistor that is sticking out of the board. Cut
    off  the excess and bend it if necessary to make sure it  does  not
    stick up enough to touch the RF sheild when you put it back on.

    Step 8) Check everything once more, and then partially  reassemble
    your ST. In other words,  put the board back in the sheilds and
    set it in the plastic bottom but don't put in the screws or  bend
    the little tab-things back yet.  Hook up everything (disk  drive,
    power supply, keyboard,  etc.) and go test it out.

    If  you  get  a normal desktop and everything  works  the  same  as
    before,  with the exception of a new entry in the pull-down  menu's
    ("Blitter"),  then you should be good to go.  Otherwise, you have a
    not  very  fun time ahead of you,  and you're on  your  own.  Well,
    that's not true, you can check these schematics I've drawn for you,
    and I'll even give you my name,  address,  phone number,  and GEnie
    mail address. I'll try to help if I can.



THE CONNECTIONS
---------------

Now,  just  in  case you can't view/print Degas pics,  here's  a  list  of
connections as they should be when you complete the procedure:


   Blitter                  68k CPU
  ---------                ---------

   28 BGI--------------------11 BG                   GLUE
   29 BGACKO-----------------12 BGACK             ----------
   37 BGO-------------------------------------------27 BGI
   40 BGACKI---------------------+------------------41 BGACK
                                 \
                                 < 4700 Ohm Resistor
                                 <
                                 /______________+5VDC


Well,  that's it. These are definitely verbose directions, but I sure wish
I had a set of verbose directions for just about every  electronic project
I've done. If you are in a philanthropical mood and  want to contribute to
the  author for his time and sanity spent,  send  whatever you  feel  like
(yeah, right). Or if you have a question, I can  be reached these ways:



                        Erik Muldowney        Genie: E.Muldowney
                        109 Poquito Rd.
                        Shalimar, FL 32579    Phone:[phone]


This  file may be reproduced,  retransmitted,  sung to music  or  whatever
turns you on as long as you don't alter it.


                                ~~~OOOO~~~