RCA COSMAC 1802

General Information

The fundamental architecture and technology of the 1802 was the same as the CDP1801. It was silicon gate CMOS and had similar packaging. The 1801 was slower at 2Mhz initially and then 4Mhz (1802 at 6.4Mhz). The 1802 (91 Op Codes) added many instructions, but was software compatible with the 1801 (59 Op Codes). The 1802 instruction additions beefed up the processors math and branching capabilities. The COSMAC architecture is classified as 8-bit (accumulator was 8-bit). However, the registers were 16-bit (and 8-bit) and processor had 16-bit addressing. The register oriented architecture made for very clean efficient programming. 

The 1801 was introduced in early 1975 and the 1802 in early 1976. The 1801 microprocessor and the COSMAC architecture were the first based on CMOS chip technology. CMOS chips could be suspended to save battery life, operated in extended temperature ranges, and were more tolerate of electronic interference. It is no wonder that the COSMAC was the first microprocessor in space. The 1801  flew on an OSCAR satellite launched in 1978. Other COSMAC spacecraft include  UoSAT-1, UoSAT-2, later DMSP, Voyager (3 1802's), Dynamics Explorer A & B, Viking, Galileo, and the Space Shuttle (TV Systems). The COSMAC's that flew in space were space/radiation hardened versions using a CMOS/SOS chip technology. These radiation hardened versions were developed in conjunction with the Sandia National Laboratories. The 1802 was likely the first microprocessor used as a nuclear weapons controller.

While only a few hundred COSMAC's flew in space, they had wide commercial use. For example, they were used in Chrysler electronic ignitions, RCA and Radio Shack video games, RCA video terminals (VP3301 & 3), Elf computers, and ETI-660 computers (some sources list the Dream 6800, but it was MC6800 based). The COSMAC Elf was introduced as hobbyist's project computer in 1976 in a series of Popular Electronics magazine articles. RCA latter developed its own "Elf" named the COSMAC VP-111 (shortened to VIP). The Elf still has a large following and many websites are dedicated to it. The 1802 led the microprocessor market in shipments at it peak popularity in 1977.

Thanks to Bob Mills for contributions to 1802 space applications history information.

Production

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General Comments

Related Chips

RCA 1801, RCA 1804, RCA 1805, RCA 1806

1821 (1024x1 RAM), 1822 (256x4 RAM), 1823 (128x8 RAM), 1824 (32x8 RAM), 1826 (64x8 RAM), 1831/2 (512x8 ROM), 1833/4 (1024x8 ROM), 1835/6/7 (2048x8 ROM), 1851 (Programmable I/O Interface, 1852 (8-bit I/O Port), 1853 (n-bit Decoder I/O Interface), 1854 (UART), 1855 (multiply/divide coprocessor), 1856 (4-bit memory buffer), 1857 (4-bit I/O buffer), 1858 (4-bit latch w decoder), 1859 (4-bit latch w dual decoder), 1861 (Video display controller), 1862 (color generator), 1863 (Programmable tone generator), 1864 (PAL interface), 1866, 1867, 1868 (latch/decoder memory interface), 1869 (Video Interface System, Address and Sound Generator), 1870, 1876 (Video Interface System), 1871 (Keyboard encoder), 1872, 1874, 1875 (8-bit I/O Port), 1877 (Programmable Interrupt Controller), 1878 (Dual Timer), 1879 (Timer), 1881, 1882, 1883 (Latch w Decoder Memory Interface)