The older
Palm Pilot models where the "PalmPilot" with 516Kb ram and the "PalmPilot Pro" with 1Mb. Besides the limited
memory, they only had 2bit grayscale and the
Operating System burned in
ROM, making upgrades impossible. Almost all new software still run on these old machines.
A bit of do it yourself soldering can expand the memory to 1Mb and 2Mb for PalmPilot and PalmPilot Pro respectively.