Amstrad User Group
Amstrad User Group
Memory expansion of a PCW 8256
Requirements: 256 kilobytes of memory in 8 integrated circuits, type 41256 with an access speed of 100-150 nano seconds. The labels on the ic will therefore vary from 41256-10 to 41256-15. These chips may be used and a twisted connector pin (shown on the picture) does not really matter. It is not recommended to mount chips with different access time but it does not matter when they differ in speed from those already mounted in the lower 256 kb.
Upgrading memory itself is fairly easy. Always avoid the build-up of static electricity and never touch the connector pins of the chips: only touch the sides of the chips. Wearing a special wristlet to avoid static electricity or discharging your body by touching (an unpainted piece of) the radiator before you begin working is a wise precaution.
Naturally you need to remove the plug from the mains (in fact, it is even recommend to do this a few hours before so that any built-up tension can reduce). Then remove the plastic casing from the back of the Joyce (6 screws) and place the machine monitor-down on a soft surface (a towel would do nicely).
Then proceed by removing the main board from the PCW by disconnecting the following cables or connectors:
- One black and one blue connector.
- The data cable of the disc drive(s).
- 1 Or 2 power connectors (depending on the number of drives fitted).
- One large 5-pin connector from the card that contains the power supply.
- The bayonet locks from the main board on the top and bottom of the casing.
Only touch the main board by the sides on spots where there are no connections or pcb-parts, to avoid static electricity or other kinds of electric or electronical damage.
Place the main board, you removed from the PCW, on a clean and flat surface in order to fit the memory expansion.
The part where you have to fit the 8 chips can be recognised easily: the 8 memory chips already fitted are located directly next to the 8 empty sockets that will contain the expansion chips.
Study the board carefully and notice the notches on the side of the sockets that indicate the direction to insert the memory chips. Notches are always used in electronics to indicate the direction: not really necessary here because by studying the 8 chips already mounted you can ascertain the proper direction already.
Now gently click the integrated circuits in the expansion sockets. I find the 'tilt-method' to work best: work from top to bottom and first guide the bottom line of ic-pins into a socket. Then make a tilting movement and gently insert the top row of pins in the sockets. This may sound simple but usually you will get the feeling for it when you are working with chip number 8... The trick is in the attitude: be serious but not over-cautious in the process. As you can see from the first picture, chips can handle some damage: the ic stood the bent pin and functioned properly after it had been bent back into shape. A great tip: use a ruler or something similar to bend pins properly and efficiently back into shape. Never touch the metal pins: static electricity is the one thing that can damage a chip easily and beyond possibility of repair.
After you have fitted the eight memory expansion chips you need to perform one more task. Study the board again and locate the dip switch SW101. A dip switch is a tiny block containing miniature dip switches, 4 in this case: the photo shows the switch within the circle. The switch is now set to 256 kilobytes memory and you need to set it to the 512kb setting.
The proper setting for 512 kilobytes is: A and C off, B and D on. The position of OFF and ON is indicated on the PCB circuitry. Do note, however, that there is an early model around of the PCW 8256 that does not have dip switches but has a set of 4 welded wires that need to be changed. Contact us for assistance when you have a model with welded wires rather than a dip switch. After you have completed the operation you reassemble the Joyce in reverse order and boot the machine. The evidence of the memory expansion should show up during the first boot already: the RAM disc M must now display a total of 368kb. To be sure you may copy drive M to it's full capacity with dummy files and, when this process completes without problems, then you can safely assume that everything went well.
To the main PCW-page.
