The RCA 1802—which is actually the one-chip implementation of the earlier two-chip RCA 1801—has a static CMOS design with no minimum clock frequency, so that it can be run at very low speeds and low power.
Although the faster version of 1802 could operate at 5Mhz (at 5V, faster at 10V), it was usually operated at 3.58Mhz/2 to suit the requirements of the 1861 chip which gave a speed of a little over 100,000 instructions per second.
The 1802 was also availible fabricated in Silicon on Sapphire which gives it the radiation resistance necessary for space applications and the 1802 was used in the Voyager, Viking, and Galileo spacecraft.
