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R > RCA > SuperElf


RCA
SuperElf

I made a RCA SuperElf, by Tom Creviston:
1977. I read the article in Popular Electronics (later Eletronics, Now!) and etched the board, bought chips, soldered and populated. I taught myself binary, hex and machine language with the hex keypad, load, save, run and single step push buttons, 256 bytes (!) of memory and dual 7-segment displays.
I believe I spent $250-300 in this effort as well as hundreds of hours. I remember that since the RCA1802 processor was CMOS I could run the thing off of a battery for days at a time. The board I etched was from the P.E. plans so it had 3-4 "card slots". I bought (mail order) 2 x 4K RAM cards for $80 apiece and a "Super IO card" for another $40(?) that held 2 RS-232 serial ports as well as two toggle pins direct from the processor that were used for input and output to two cassette decks (8" floppies were available but were over $1000 apiece).
I accquired an ADM3A Lear-Siegler dumb terminal ($400) and an Integral Data Systems Paper Tiger printer ($400) to make it a real computer. So by the time I was done, I had spent about $1250 for this 8.25KB machine. Oh, I almost forgot the $300 1200baud Supermodem.
There was a Canadian-based (Ontario) fan-club (COSMAC, I think) that published a newsletter in which many of us published our programs. I wrote one that was a simple screen typewriter (it used self-modifying code to circumvent the small memory space). Someone else wrote one called "Indigenous Music" that cycled bits back and forth through the registers of the processor and then spit them out the CD4 pin of the 1802 attached to a speaker. Seemed like the computer was making up its own music. I learned a lot from that machine that I carry with me to this day.
.


About the Q line, by Richard Dienstknecht:
In your description of the Super Elf you write that sound was produced by software over the Q line.
This is true, but the Q line had some more important functions. It was the only I/O line available which could be controlled by the CPU directly. Therefore it was used primarily to generate the signal for recording programs to tape as well. Often serial terminals were connected to an Elf (both Netronics and Quest had terminal kits) and the Q line served in a triple function as RS232 C serial interface, again driven by software.

Usually there were additional switches to mut the speaker or to cut off the data to the terminal since you did not want garbage on your terminal's screen while saving a program or playing sound. Also you would not want to hear the data going to the tape recorder or the terminal. And using more than one of these at once was not possible.
Again all this is for a typical Elf, but modifications to solve these problems were possible at the price of sacrificing compatibility.





 
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