The Museum of HP Calculators HP began designing a new CPU called
Saturn and series of calculators to follow the HP-41C but these
designs became quite complex so they designed another series of
midrange calculators based on improved HP-41C technology as a
short-term measure. The CPU for these new machines included
61Kbits of ROM, 2.2Kbits of RAM, an LCD driver and a low-battery
detector on-chip. To improve on previous designs, HP developed a
new CMOSC process with design goals including: Previous HP's had
a flexible sheet under the keyboard to protect the electronics
from minor spills and dirt. The 10C series took this further by
having a single large sheet of film under the keyboard that
wrapped around the electronics and overlapped at the back. This
sheet consisted of three bonded layers: the outer layers were
nonconductive, but the center layer was conductive. There was
also an inner conductive film surrounding the main circuit
board. These films gave the CMOSC chips a high degree of
electrostatic protectio