Hobbyist Computing 1977:
A COSMAC Elf Implementation

This is an implementation of the COSMAC Elf, constructed in 1977 going by the labelling and component date codes. It presents an example of early hobbyist computer construction. Printed in the foil pattern is "G. VENTURI Tech 77" and in handwriting "AW Kits 77". As the unit originated in the Vancouver, B.C., Canada area, it was likely a project at Kitsilano High School.

The COSMAC Elf was a microprocessor trainer based on the RCA 1802 CMOS microprocessor. Construction articles for the Elf were presented in the August & September 1976 issues of Popular Electronics, with additional articles in March and July 1977. The basic Elf was a minimal stand-alone system, complete with front panel for loading programs, input and output. Aspects of the 1802 - primarily the built-in DMA technique - made it possible to achieve this with only 8 SSI/MSI ICs in addition to the 1802 processor and two 2101 (256*4) static RAM chips, for a total of just 11 ICs (see schematic).

The history and details of the Elf are covered at other sites such as those linked below.

The PCB layout of this implementation is different than that of the Popular Electronics articles, involving 2 boards - an MPU board and a front panel board - instead of the single board of the P-E articles. Somewhat oddly the MPU board has "SUPER ELF" in the foil, although the unit as a whole is very much the simpler original Elf. The unit needed a cleaning, some of the wiring and soldering cleaned up, a few components replaced and the power supply redone, and it was functioning.

See the Sherwood Micro/CPU-100 FM receiver for an example of embedded use of an 1802 processor in the mid-1970s.

External Links

  1802 Instructions | Programs | Schematic | Log
2011 Aug