Way back in the days when most microcomputers were beyond the means
but the most dedicated hobbyists, Popular Electronics published in its
1976 issue an article entitled 'Build the COSMAC "ELF": A Low-Cost
Experimenter's Microcomputer'. If you're not lucky enough to have
issue, you can read Bill
Richman's scan of it. (local
The Front Side. It's pretty close to the original (Part 1) ELF. I do have an 1861 video chip as was used in the revised (Part 4) design, but I wanted to build the original version. Originally I had used a laser-printed front panel, but members of the cosmacelf mailing list pointed me at a source of dry-transfer letters, so I redid it the authentic way (Detail of switches and panel lettering). Another nice thing that happened after I first built it was that I located some authentic RCA CMOS logic ICs for a number of the types used in the ELF.
The differences in this rendition from the original are:
Here's a close-up that shows exact parts placement I used. This layout was arrived at by starting with the article picture and then placing the parts where the wiring made the most sense. If you intend to use an 1861, now's the time to make room for it!
Here's a template for cutting and drilling the aluminum switch panel in BMP format at 300 DPI.
The Back Side. Construction is wire-wrap throughout. There is no photo of the original wiring, but I suspect that it was a point-to-point mess, perhaps using a wiring pencil. Here the ICs are in WW sockets and the small components are soldered to posts. It ran the first try!
|CDP1802CE||eBay or cosmacelf mailing list|
(note that the Jameco part # is not the hexadecimal version)
|Salvaged from some surplus circuit boards
A equivalent part with a different size, pinout and orientation is the TIL311 available from Unicorn Electronics.
|SY2101 SRAM||Unicorn Electronics|
|Phenolic perfboard||Radio Shack part # 276-1394|
|diodes||Radio Shack part # 276-1122 or 276-1620|
|Aluminum sheet, black enamel, clear varnish||Ace Hardware|
|Dry Transfer lettering||1/8" white lettering from DATAK or Woodland Scenics|
|CMOS, sockets, etc,||various web electronic dealers, junk box|
|Resistors (Carbon composite)||Mouser electronics|
|Toggle Switches and covers||Digi-Key (or Radio Shack)|
|Pushbutton switch and button||Digi-Key (or Radio Shack)|