Elektor_Mag_-_January-February_2021

lektor January & February 2021 43

timer, a music box and an I^2 C-bus scanner. Both expansion boards
can be seen in Figure 4.

“The first version of MyNOR on a ‘real’ circuit board was not quite
perfect. Nevertheless, this version (including the 7-segment expan-
sion) is still serving a purpose: I converted MyNOR v1.0 into a
teeth-brushing timer for my children (Figure 5).

“At the moment I’m busy with the further ‘discretising’ of the
computer. Because the entire MyNOR computer comprises of

only 22 ICs, it is a nice challenge to replace the 19 logic ICs with

discreet transistor circuits. The first experiments toward this goal

are showing much promise. Figure 6 shows two ICs built using

individual transistors.

“By the way, I’m not the only one who is busy with DIY CPUs. Many

of us have come together in the ‘Homebrew CPU Webring’; a visit

to their website [3] is certainly worthwhile.”

200552-04

Figure 5: The toothbrush timer consists of a MyNOR v1.0 plus the 7-segment
board v1.0. The device underneath the timer is, by the way, a high-end
receiver (FM and DAB+) with integrated 11-band equaliser and touch
controls that Dennis built last year.

Figure 6: Two ICs implemented using individual transistors. The original ICs

are also shown for comparison (74HC541 and 74HC74).

[1] MyCPU: http://www.mycpu.eu

[2] MyNOR: http://www.mynor.org

[3] Homebrew CPU Ring: http://www.homebrewcpuring.org

WEB LINKS

TO BE CONTINUED?

Would you like to know more about DIY CPUs? Let us know

via [email protected] and perhaps we will devote a more

comprehensive article to this topic in the future.

Questions or Comments?

Do you have questions or comments regarding this article?

Then email Elektor at [email protected].

Contributors

Text and photos:

Dennis Kuschel

Translation: Arthur de Beun

Editing: Stuart Cording

Layout: Giel Dols

About the author

Dennis Kuschel first came into contact with electronics when, as a six-year old, he exchanged a bag of lollies for a faulty transistor

radio with a class mate. To the great surprise of his parents he managed to get the radio to work after a short period of time. At the

moment, Dennis works as a hardware developer for a German camera manufacturer. There he designs circuits and 10-layer Starrflex-

HDI circuit boards and programs complex IP-cores for FPGAs. Privately he prefers to go into the opposite direction. “Keep it simple”

is his motto — the smaller the number of parts involved, the less there is to go wrong.