Last update: 2009-05-07.
The following pictures illustrate how to add extra RAM chips to a Minimig V1.1 board. When you click on any picture below you should see a higher resolution version of it.
It's possible to add only one memory chip to increase total available memory by 1 MB. In such a case its Chip Enable line (the leg #6) must be connected to the pin #7 of the SPARE I/O header.
You will need the following tools:
1. A fine tipped soldering iron.
2. A soldering wire with rosin core (preferably Sn-Pb compound 0.5-0.7 mm in diameter).
3. Soldering rosin flux (a gel in syringe is the most convenient). Actually it's the most important component of the soldering process. It protects the melted solder from oxidation and allows it to easily stick to the soldered surfaces. Without it it's not possible to do the described job.
4. A flat nose pliers. They are needed to straighten and bend the legs of the memory chips.
It's important that they have flat surfaces at the top of the nose. Otherwise it's possible to destroy the legs of the memory chips.
5. A solder wick. It's required to remove solder bridges which will be accidentally created between the legs of memory chips.
5. A piece of insulated thin wire (Kynar recommended) and some other tools like small screwdrivers, small tweezers and scissors (not shown).
You need 2 pieces of 512Kx16 bits (that's 1 Mega bytes) memory chips in 44-pin TSOP-II package. The original Minimig V1.1 boards manufactured by Acube are equipped with CYPRESS SEMICONDUCTOR CY62157EV30LL-45ZSXI chips. You can buy them at Farnell (Order Code: 1650069). Also available at Mouser (Mouser Part No: 727-CY57EV30LL45ZSXI) and Digi-Key (Digi-Key Part Number: 428-2079-ND).
Mark leg #6 as this one won't be connected to the existing memory chip on which this one will be piggy backed. The leg #6 will be connected with a wire to a pin of the spare IO header. The legs are counted counterclockwise beginning from the left bottom corner .
Now we will shape the legs so they will fit on the top of the existing memory chips. Using pliers straighten the bottom part of the gull wing shaped legs towards the bottom of the chip. Do this carefully and gently and do your best not to break any of the legs.
Repeat the operation for all the legs including the marked one. You will get all legs pointing the direction of the bottom of the chip.
Since the already bent legs are not long enough to touch the legs of the existing memory chips (on the Minimig board) we have to bend the legs in the other direction to lengthen them later.
Repeat the above operation for all the remaining legs. You should have all the legs flattened. If the marking of the leg #6 was degraded during the previous action fix it now since it will be required in the next step.
Now using some hard and flat surface (a flat screwdriver or scissors) gently bend every flattened leg down except the marked one. Do this leg by leg. Do not hurry. Take care not to break any of the legs.
Make sure all legs are lined in a row. If they aren't fix them.
Notice that the leg #6 is not bent.
Now position the new memory chip over the existing one. You can install only one extra chip but this must be done over the Minimig's memory chip marked as IC7 and the leg #6 has to be connected to the pin #7 of the SPARE I/O header. In this way you will add only 1 MB of extra memory.
It's advised to do the mod in two stages. First install the extra memory chip over the IC7 and verify if the system works correctly. Then if everything is ok install the second extra chip over the IC6.
Align the new chip over the existing one. Make sure all the legs fit perfectly. If any is misaligned remove the extra chip and fix the nonaligned legs (bend them sideways with a knife if required).
Verify the alignment from different angles.
Now we will need a soldering iron. Switch it on and set the temperature to approximately 360 degrees Celsius. Apply a small drop of the soldering rosin flux to a leg located at a corner.
Melt a small quantity of solder and apply directly to the corner leg. If you accidentally bridge two legs don't bother right now. We will fix it later. Now it's more important to fix mechanically the extra memory chip over the existing one.
If everything goes well you should have the first leg soldered down.
Now apply the flux to the opposite corner leg.
And solder it down.
Repeat the operation at the other side of the chip. Apply the flux.
And the solder.
Repeat the operations for the last corner leg.
Now apply the flux to all remaining legs on one side.
And solder them one by one.
You should have all the legs soldered to the appropriate legs of the chip below.
Now repeat the operation at the other side of the chip. Apply the flux and solder.
If accidentally some solder bridges are created you can easily remove them using a solder wick.
Apply small amount of the flux to the solder bridge and place there the end of the solder wick.
Now heat the solder bridge with the soldering iron tip to melt it down.
The solder will be sucked by the wick. You may cut off the end of the wick to have it ready for the next use.
You may need to apply again the flux and solder to recreate the solder joint. Inspect all legs visually and remove any remaining bridges. If you find a break between legs of the new chip and existing one apply the flux and solder to make connection. You may need a magnifying glass or a digital camera with macro shots to have a better view.
Now when the new memory chip is in place we will connect the remaining leg #6 to the appropriate pin of the SPARE I/O header. We will need a thin wire (the Kynar branded are very good). Cut a piece of sufficient length and remove insulation at its ends.
Apply some flux and solder to the leg #6 and create a solder joint with the wire.
The other end of the wire connects to the appropriate pin of the SPARE I/O header. Make a solder joint at the connection to the header (not shown in the picture below). The first piggy-backed memory chip should have its leg #6 connected to the pin #7 of the SPARE I/O header. The second piggy-backed memory chip should have its leg #6 connected to the pin #3 of the SPARE I/O header. The pins of the SPARE I/O header are counted from the marked one (most left-bottom pin in the picture below) in a way that the odd-numbered pins are in the bottom row and the even-numbered ones are in the top row. The numbers increase to the right.
You can clean the PCB from the remains of the flux using a small brush and isopropanol (IPA - isopropyl alcohol) or special PCB cleaner.
The extra memory chips are supported by the FPGA firmware from 2009. The latest version is FYQ090421. You must be aware that the former releases may not work at all.
You must enable the extra memory by changing menu settings in Settings->Memory->CHIP/SLOW to the desired values. Maximum is 2 MB of Chip and 1.5 MB of Slow when no Action Replay is active (when the Action Replay ROM is loaded it decreases the total available RAM by 512 KB).
You should verify if the memory works correctly with a memory test program like Advanced Amiga Analyzer by Wilcom Australia. If errors are detected make a visual inspection of the soldered chips and fix breaks or bridges.
It might happen that the system won't boot again, you may no longer see a bootloader screen (although blue background should always be visible). In such a case it means you have solder bridges between memory legs, just locate them and remove them. Nothing to worry about.