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General Information

The COSMAC 1802 was RCA’s first single chip microprocessor. The 1802 is a single chip implementation of the two chip 1801. 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, Dynamics Explorer A & B, 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.


Early 1975
Designers Lead Designer: Joe Weisbecker, Team Lead: Jerry Herzog


Type Data Word Address Space Clock Instruct- ions Assists Reg’s  GP Reg’s Math Reg’s Index IO Ports   Stack Interrupts Memory
2 Chip CPUCMOS 8-bit 64K 2.5Mhz, 5Mhz,  and 6.4Mhz 91 NA 16×16-bit or 32×8-bit 1 NA 8 Ext RAM 1 Level NA


Chip Name


On-Chip Identification


General Comments

CDP1802D white ceramic, silver lid, 40 gold side braised pins CDP1802D   Standard operating range: 4V to10.5V. The ceramic “D” versions have an operating temperature range of -55o to 120oC
CDP1802CD gray ceramic, silver lid, 40 gold side braised pins CDP1802CD CDP1802CD.jpg (17718 bytes) “C” suffix versions have a lower voltage range: 4V to 6.5V. Max clock was limited to 2.5Mhz
CDP1802AD white ceramic, silver lid, 40 gold side braised pins CDP1802AD   “A” versions increased max clock to 6.4Mhz. Introduced 2nd Q 1981
CDP1802ACD white ceramic, silver lid, 40 gold side braised pins CDP1802ACD    
CDP1802BD white ceramic, silver lid, 40 gold side braised pins CDP1802BD    
CDP1802BCD white ceramic, silver lid, 40 gold side braised pins CDP1802BCD    
CDP1802E black plastic, 40 tin leads CDP1802E   The plastic “E” versions have an operating temperature range of -40o to 85oC, 
CDP1802CE black plastic, 40 tin leads CDP1802CE CDP1802CE.jpg (26525 bytes)  
CDP1802CEX black plastic, 40 tin leads CDP1802CE X CDP1802CEX.jpg (24152 bytes) An “X” prefix on 1802’s indicates a engineering  sample or prototype (usually “X-“). If the “X” is used as a suffix, it indicates the chip has undergone extended burn-in time. (Thanks to Mark Graybill for clarification on X labeling)
CDP1802AE black plastic, 40 tin leads CDP1802AE    
CDP1802ACE black plastic, 40 tin leads CDP1802ACE    
CDP1802BE black plastic, 40 tin leads CDP1802BE    
CDP1802BCE black plastic, 40 tin leads CDP1802BCE CDP1802BCE.jpg (26347 bytes)  
CDP1802AQ black plastic QUIP, 44 tin leads CDP1802AQ   The plastic QUIP “Q” versions have an operating temperature range of -40o to 85oC, 
CDP1802ACQ black plastic QUIP, 44 tin leads CDP1802ACQ    

Related Chips

Related Chips

RCA 1801, RCA 1804, RCA 1805, RCA 1806

Second Sources

Hughes, SSS

Support Chips 1821 (1024×1 RAM), 1822 (256×4 RAM), 1823 (128×8 RAM), 1824 (32×8 RAM), 1826 (64×8 RAM), 1831/2 (512×8 ROM), 1833/4 (1024×8 ROM), 1835/6/7 (2048×8 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)