| From: DECWRL::"[email protected]" 27-OCT-1992 23:56:56.03
To: oldtmr::wallace
CC:
Subj: Re: D.I.Y. 4 Meg upgrade???
One of the ultimate ironies of the Atari ST system is that
the computer is not upgradeable. I'm sure that many people from
other computer platforms would be very quick to agree. Many
others, such as Dave Small, and probably the people at ICD INC
would take some small exception to this idea. I too would have to
take a minor exception. Because of the relatively closed
architecture of the ST this computer system has become a hackers
heaven. It is with this in mind that I have written this recount
of my experiences using SIMMs to upgrade STs to 2 1/2 megs.
It seems like each time I read an article about upgrades
there is a long warning about warranties and technical competence.
Why should I care if you ruin your computer? As far as your
warranty goes, if you remove the screws on the bottom your warranty
is void. My upgrade will cause your warranty to explode and
possibly ruin your computer desk in the process. There is the
small reminder that since the warranty is only 90 days in the
first place, the odds of your warranty being valid at this time
are nill. One small consolation, if you do ruin your computer
while attempting this upgrade you can always buy an STe and use
the SIMMs there.
The reasons I developed this particular style of upgrade are
two fold. The first is that I just wanted to see if I could do
it. The second has to do with my personal feelings about sockets
that plug into existing chip sockets and cause permanent damage.
There are a couple of advantages to my upgrade techniques.
1} I use SIMMs, which are noted for their reliability.
2} All connections are soldered which means no sockets to ruin and if
properly done provides extremely reliable long term operation.
Since you are probably going to try this anyway, you should
go ahead and get yourself a pair of 1 meg x 8 SIMMs. If you
should happen to get the 1 meg x 9 SIMMs, that is ok too. The
speed isn't that important, but it is hard to find a set of SIMMs
these days slower than 100ns anyway. While you are in the getting
mode, get yourself a few feet of 28 gauge Kevlar wire such is used
for wire wrapping, a few bits 8" of 7 stranded hookup wire, a
1/8 w 33 ohm resistor, double sided mounting tape, a hot glue gun,
plus a Fluke Model 73-77 digital meter, plus a good solder sucker.
You will also need a decent temperature controlled soldering
iron running between 750 and 800 degrees.
Take your 25 watt Radio Shack type iron and throw it away while
you are at it. Those small and unregulated irons are a good
source of just the right types of static known for killing CMOS
circuitry dead. I should also mention the fact that the longer a
soldering iron remains on the circuit board, the greater the
chances are that you will begin destroying the foil patterns.
The major problem I have encountered while upgrading STs is
the numerous version revisions. There are no fewer than 6
different styles of mother boards and many of them use different
circuit symbols for the various components. For this reason I will
not be referring to any of the components by their circuit
symbols. All references will be by component name, such as the
MMU, or the upper and lower RAM banks. I simply have to assume
you know what your are doing.
I begin the upgrade by removing the mother board from the
computer and placing in on an anti-static workbench. Depending on
the model of computer, the upper or lower bank of ram chips must be
removed. By upper bank I mean the row of chips connected to the
CAS1, and RAS1 lines from the MMU chip. You may verify this by
measuring from pins 18, 21, and 22 of the MMU chip. CAS1 H = 22,
CAS1 L = 21, and RAS1 = 18. The corresponding locations of the
CAS and RAS lines on the ram chips are pins 15 for CAS and 4 for
RAS.
NOTE: ** RS. The banks that you use does not matter..**
The ST uses two rows and four columns of ram chips in their
memory addressing scheme. The Row Address Strobes ( RAS ) are
labeled RAS1 and RAS0, and the Column Address Strobes ( CAS ) are
labeled CAS1 H, CAS1 L, CAS0 H, and CAS0 L where the H and L stand
for High and Low. All the lines using the 1 are related to the
the upper row and the lines labeled with the 0 are used in the
lower row.
You will probably not find the above mentioned labels printed
on your particular mother board. The only time I remember seeing
this done was on the 520ST with modulator. Don't expect it.
If you are wanting to do this upgrade on the early 520 you
should remove the entire set of ram chips. Your final upgrade
will be 2 megs instead of 2.5. There is just no clean way to
install all the wiring needed to installed chips.
Once the ram chips are removed it is time to mount the SIMMs
and prepare the wiring. On the machines where the ram chips are
mounted under the keyboard, there is a good place to mount the
SIMMs right above the upper bank of ram chips. I use strips of
double sided adhesive foam which I attach to the back of one of
the SIMMs. I then stick this SIMM to the mother board. When the
SIMM is mounted it is about 3/4 inch above the spot where the ram
chips were removed. I then take another strip of adhesive foam
and cut it to a width of 1/4 inch. This strip is placed on the
top rear of the SIMM I just mounted on the board. Now I carefully
place the second SIMM directly over the first. It is important to
line the two SIMMs up so that they match exactly. When completed
I have the two SIMMs stuck together, with one on top of the other.
From this time on, consider the top SIMM to be the "High" and the
bottom SIMM to be the "Low" column.
For the STs with the ram under the keyboard, the upper bank
of ram chips just happens to be the ones farthest away from the
front of the machine. It also happens that the "High" column is o
the left and the "Low" column is on the right. To make
remembering easier I use a marker and mark the center between the
two columns. That make eight on the left and eight on the right
side of the mark.
If you have one of the STs with the ram under the powersupply,
you will need to use the Diode Option of say a Fluke Digital meter
73-77 and verify the locations of the upper and lower banks.
While I have looked at one of these beasts I have not
done an upgrade on this particular style so I cannot suggest
a location for the SIMMs.
** RS. I suggest infront of the power supply, remove the Rams next to the
Cartridge socket, the SIMMS were stuck on top of a IC there, with
also the use of a Hot Glue Gun to hold the ends of the SIMMS in
place.. **
The following pinouts will be critical to your successful
upgrade: 1 meg x 8 SIMM
0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3
1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
V C D A A D A A V D A A D A A D A A N D W V D N D N R V V V
C A Q 0 1 Q 2 3 S Q 4 5 Q 6 7 Q 8 9 C Q E S Q C Q C A C C C
C S 0 1 S 2 3 4 5 S 6 7 S C C C
256K DRAM Pinout
1> A8 16> VSS
2> Din 15> CAS
3> WE 14> Dout
4> RAS 13> A6
5> A0 12> A3
6> A2 11> A4
7> A1 10> A5
8> VCC 9> A7
If you notice, there is no A9 on the ram chips. This is the
new address line and special consideration is required. I will
cover this further on.
I start by making a check list numbered from 1 to 30 with two
columns, one for the upper and one for the lower columns.
PIN 1 and 28,29,30 also..
Beginning with pin 1 on the SIMMs take the kevlar wire and strip
back about half an inch. The neat thing about the wire is that it
fits perfectly into the holes on the SIMMs. Since the Vcc line is
common to both SIMMs I insert the wire into the lower SIMM and
solder it into place. I then attach the wire to the upper SIMM
and solder it. Because the Vcc line is what it is, I now use a
slightly larger gauge wire and run it from pin 1 of the SIMM to
pin 8 of the nearest vacant ram. In order to keep things neat, I
keep the wires as short as possible without any undue stress.
Do the same for PIN 30, but also connect PINS 28,29 to PIN 30,
on top and bottom SIMMs, so there are 2 Vcc lines from the
SIMMs to 2 ic pin 8's.
Since I removed the 16 ram chips I have my choice of spots
for the placement of the wires run from the SIMMs. The following
considerations should be taken into account.
The address lines A0 through A8 are common to all the chips.
The CAS lines are split so CAS H is common to the upper column
of 8 chips and CAS L is common to the lower 8 chips. The RAS
line is common to all 16 chips. The DQ lines are separate and
require special wiring.
PIN 2
The CAS line on pin 2 of the SIMMs needs to be split up. The
lower SIMM is wired to any convenient pin 15 of the lower column.
The upper SIMM is wired to pin 15 in the upper ram column.
PIN 3
DQ0 is split. The lower SIMM is run to the first chip socket
of the lower column. This should be the chip closest to the spot
previously marked as the center. Both columns run from left to
right. The DQ label corresponds to the Din or pin 2 of the ram
socket. The upper SIMM is wired to the ram socket farthest to
the left.
PIN 4
A0 should be wired from the lower SIMM to the upper SIMM. It
should then be wired to the nearest ram socket pin 5. The only
major concern here is neatness.
PIN 9 and 22
These are the Vss pins, connect lower to upper with the
Kevlar wire, then use the thicker wire from SIMM pin 9 to ram
pin 16, also do the same for SIMM pin 22 to another ram pin 16.
The rest of the wiring follows the same order listed above.
Pin 21 of the SIMM should be jumpered between the two SIMMs and
then run to ram pin 3. Pin 27 of the SIMMs is also jumpered
between the two SIMMs and then run to ram pin 4.
PIN 18
The A9 line is the new address line which is required when 1
meg chips are used. This line should also be jumpered between the
two SIMMs. Using the Kevlar wire I run to one of the holes where
the ram chips were removed. What I like to do is drop the
insulated wire through the hole and run it over near the MMU. The
idea here is to run the wire from the SIMMs pin 18 through a 33
ohm 1/8 w resistor (which you need to come up with) to pin 64 of the
MMU. I like to use a little shrink tubing over the resistor
connections since this is an outboard hookup. Using a couple of
convenient holes for wire routing simply makes for a neater job,
the hot glue gun can be used to hold this wire in place under
the P.C.B..
I follow my check list exactly and mark each connection as it
is made. Since the key to a well done job is top quality
craftsmanship, I am careful to do the best job I am capable of.
This completes the upgrade. If you want to go to 4 megs all
you need to do is make a few minor changes. Remove all the ram
chips and of course use 2 pairs of SIMMs. Wire one pair into the
upper bank position and the second pair into the lower bank
position. You do not need to do anything about swapping the CAS
and RAS positions.
I would like to suggest that you get ahold of some type of
memory tester program. There is one in the GEnie library written
by Barry Orlando which will do the job nicely. Another program
written by Willie Brown does a good job as well. It is also
possible to use NeoDesk to look at but not test our memory. With
Neo Desk simply click on the desktop info and read the screen.
there is a line at the bottom of the screen which identifies free
memory.
I will admit that once or twice my upgrades did not work at
first and required some trouble shooting. If this is the case,
you will need to double check your work. Each time I had trouble
it was caused either by a faulty solder connection..
There is one other place you may get some trouble.
If you are upgrading from 512k and the computer has never had
a memory upgrade before, there is a possibility that the MMU chip
could be bad. This can occur because the CAS1 and RAS1 lines have
never been used or tested. I ran into this problem once. It also
doesn't hurt to remove and clean the MMU and its socket. This can
pay off on the older machines.
Just in case I have inspired you to go out and do this
upgrade, let me advise you that it takes me about 6 hours to do
this job. Using a good desoldering machine to remove the old ram
chips takes about 1 hour. You could also use a fine pair of
cutting pliers and clip out the chips. This would be much faster,
but I like to save the chips for other projects. The fastest
upgrade I did was on a 520STFM where the 1040 mother board was
used. There were no ram chips to remove.
Now that it is all done, it is time to sit back and enjoy
your work. 2.5 megs is a pretty nice upgrade. The cost was
fairly reasonable, the SIMMs cost $90 to $110 a pair and 100 feet
of Kevlar wire costs about $5 bucks. The only other cost is for
the resistors and depending on the computer you will need from 1
to 4 of them. I recommend using 1/8 watt 33 ohms.
I hope that this information is of some value to those of you
who have read it. You may use this document in your club news
letters or magazines provided it is printed in its entirety. You
may not remove my byline cause I need some claim to fame. Finally
if you should choose to perform this upgrade and kill your
computer, you can always buy an STe and sell your dead computer to
me, really cheap. Heck, I can always use a few more spare parts.
Paul Gittins
Portland Atari Club, PAC
GEnie id: P.Gittins
Rogers bit...
MMU Pins. The dimple is located over pin 1.. 43________27
44| |26
61.62.63.64.65.66.67.68.1.2.3.4.5.6.7.8.9 | |
G M | MMU |
N A | |
D D | |
9 60-----*-----10
61 1 9
NOTE: 4. 33 ohm resitor goes on pin 18.. A9..
PINs 28/29 are inputs SIMMs bit 9, I connected them to
pin 30. VCC.
MMU Pins 6/7 are CAS0 and 21/22 are CAS1
NOTE: MMU Part No. C0100109-001 will not work for 2.5 megs,
only 520k, 1 meg, 2 megs, and 4 megs..
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