The US Robotics/Palm Computing Pilot is available in two models, the Pilot 1000 and the Pilot 5000. The 1000 has 128k of RAM and the 5000 has 512k of RAM. A 1MB upgrade is also available from US Robotics.
The Pilot has no RAM or ROM on the mainboard. All memory is on the single memory card. While this saves space, it is wasteful since you can't use the old memory after the upgrade.
 |
I didn't want to spend $150 for a meager 1MB of RAM. After looking at
the memory boards of the 1000, 5000 and a 1MB upgrade, I realized that
the only difference between them was which chips were installed. This
meant that I could upgrade the board if I could find the chips I
needed.
The 512k board was the easiest since I only had to add the RAM chip and move one 0 ohm resistor (which is actually a jumper connection). I called the regional office for Toshiba, and was given the phone numbers of several local distributors. The third one I called sold me a small quantity of chips. I carefully installed the RAM chip and moved the resistor. I put the board back in the Pilot and tested it. Success! This took care of upgrading Pilot 5000's. |
To upgrade the 128k board there are two issues to solve. The first problem is how to disable the existing RAM chip. The second question is, what is that weird little five pin chip at "U5?" To solve these problems, I traced the circuits on the memory board and how they connect to the CPU on the Pilot mainboard. At this point it became obvious that the 128k and 512k boards were only using half of the available data bus. This means the upgraded memory board will make your Pilot nearly twice as fast as either the 128k or 512k boards. What a nice added bonus! Also, all 24 of the address lines from the CPU are available to the memory card. This means memory cards up to 16MB are theoretically possible. The batteries would only last about a day, but it is possible.
To disable the 128k chip, I could either remove the chip or figure out how to turn it off. To turn it off would require cutting a circuit on the board and connecting a wire from the cut to another point on the board. The circuits are very close together in this area and it would be very easy to slip and completely destroy the board. Obviously this isn't the answer.
The "U5" chip appears to be a single logic gate to turn the larger memory chips on and off. I removed the chip from my 512k board and tested it. It is a single 3 volt "AND" gate.
I carefully removed the 128k chip. I used a small, low-wattage soldering iron and was very careful not to overheat the traces on the board. Then I added the new RAM chips at U1 and U2, the AND gate at U5, and a jumper wire at R2. The Pilot 1000's 128k board has been converted to 1MB!
One last thing, there are at least two versions of the circuit board. On the back of the board look for PM160-0086 REV xx or 160-0086 REV xx. The xx will be either "P1" or "B". The "P1" revision boards require an additional jumper wire when converting the 128k board.
I should point out some important things here. Obviously your warranty on the memory board will no longer be valid. US Robotics will not help you with this conversion. Don't even ask them about it. They didn't seem too overjoyed that I had figured it out. If you send your unit in for repair, I would recommend borrowing a 128k card and sending it in with that installed. If you are not completely comfortable working with static sensitive, surface mount devices please find a tech-head who is. I will not accept liability for any damage you do to your Pilot, even if you have followed the instructions exactly. More technical information about the Pilot system (including pictures, links to sources, etc.) can be found at Steve's Pilot Tech. Page (http://web2.airmail.net/srsimmon/pilot).
I want to thank the people that have given me help, guidance, and insight on this project: J. D. Sterling Babcock,crobins@worldnet.att.net, Scott R. Andress, and others.
All information contained within the magazine is ©PMN Publications 1996.