|A one meg Stacy is,
to say the least, practicaly unusable for most
tasks these days. At least for me... Therefore I
tried, with luck I might add, to upgrade my Stacy
to 4Mb. So in case someone is crazy enough to
try, this page gives a relatively crude
description on how to upgrade an Atari Stacy from
1Mb to 4Mb using a 72-pin PS/2 SIMM.
The description is, as mentioned, rather crude,
but even people with mediocre skills, like
myself, should without bigger problems be able to
go through with this upgrade.
I must mention that the Stacy was donated to me by Jo
Even Skarstein :-) I really appreciated that!
Good luck upgrading!
|This upgarde isn't actually very complex, but
because the memory is such a vital part of the
Stacy, it's very important to have a minimum of
knowledge about computer architecture, memory and
electronics in general. The reason is that with
so many wires and solder-points, it's almost
bound to be some sort of problems, and without a
minimum of understanding, one might give up too
This upgrade also requires some rather basic
soldering/desoldering skills and some elementary
knowledge about the use of multimeters.
line: You do this at your
|What you'll need
|There are a few things which are nesessary to
do this upgrade, and there are a few things that
- One 1Mb Stacy
- 4Mb 72-pin PS/2 SIMM - FastPage, NOT
EDO!!!! (I actually used an 8Mb SIMM)
- More than 35 wires - approx. 10 cm long
- Soldering iron
- Different screwdrivers - to open up the
- A 72-pin SIMM socket - Recommended
|Open up the Stacy
|I will not explain to
you how to open up the Stacy, partly
because that's boring work, and partly
because I happen to own a secondhand
Stacy which doesn't have all the
shielding inside. So there you're at your
Remove the screen, the shielding
and the keyboard. There's probably no
need for you to remove the hard-drive,
floppy or hd-controller.
You should now have something like
this in front of you:
the card you have in the front looking
Take out the 3 screws that
hold this card and pull the card off the
motherboard. It's much easier to work
with it that way, as you don't have to
drag the whole Stacy around.
Note: This is in fact a 2/4Mb card. I
had to borrow this picture from Jo Even.
|This is the finished module:
Nice, isn't it?
Well... Remember to tape the module good to
prevent short circuiting the machine! Put the
Stacy back again... The module should fit nicely
between the memory-card and the PSU-card. Turn
the Stacy on and hope for the best!
You should now have a working 4Mb Stacy!
|These are the most likely causes for trouble:
- Wrong type of SIMM
- Broken SIMM
- Bad soldering
- too little GND or +5V to SIMM
- Bad assembly of Stacy
- Switched wires
- Soldered to the wrong pin
So what can you do?
- Check that you have a correct SIMM-type,
and that it actually works. Use your
imagination on this one.
- Check the connections for bad soldering
- Check if you've soldered to the correct
- Question my information
|The data lines can be
found at the Shifter-chip (See picture).
Pin 3-10 is D0-D7 and pin 12-19 is D8-15.
Check that these corresponds with the
data pins on the SIMM. Remember that
there should be a 33 Ohm resistanse
between these points!
|The address lines can be
found at the MMU (C025912-38 - See
picture). Pin 59-54 is MAD0-MAD5 and pin
60,62,63,64(or whas it 66?) is MAD6-MAD9.
Check that these corresponds with the
address pins on the SIMM. Remember that
there should be a 33 Ohm resistanse on
these lines too!
The write enable line can be found at pin
23 on the MMU. Check this pin against pin
47 on the SIMM. Again 33 Ohm.
|The CAS0L, CAS0H, CAS1L,
CAS1H, RAS0 and RAS1 originates from pin
7,6,21,22,8 and 18 on the MMU, but goes
through a bus driver-chip (74LS244 or
similar) located nearby the MMU (See
picture). The signal from this chip is
fed through six 33 Ohm resistors before
they reaches J3 (a.k.a J25 on the