With the PC-1251, Sharp started off their product range of really tiny pocket
computers. It was the third original design after the PC-121x and
Contrary to its predecessors, it was really pocket sized, measuring only 135 x 70 x 9.5 mm. Nevertheless, it featured a 24 character display, and with 4 KB RAM it even outclassed the PC-1500 basic version. The major drawback of the new design was that the tiny keys are only compatible with pointed fingers.
The PC-1251 was based on a new 8-bit CMOS micro processor, the SC61860, which
was mounted on the main PCB together with the display driver chip SC43536. On an additional small PCB, 24 KB ROM (LH532917) and 4 KB RAM (two HM6116 2k x 8
chips) were located. A new feature was the so-called "reserve memory" which
allowed to assign often used BASIC commands or functions to 18 of the
Together with the PC-1251, the CE-125 thermal printer and micro cassette
recorder unit was introduced. With integrated NiCd accumulators, it was fully
mains independent and made the 1251 into a very compact mobile computing system. The CE-125 also featured an additional tape interface for external tape recorders.
The PC-1250 was the same machine as the PC-1251 but with only 2 KB of RAM.
Thanks to Roman von Wartburg and his site for information and picture.