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8-bit CPU reset circuit and power supply tips (Patreon)

Published:
2017-05-29 16:49:35
Imported:
2026-06
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8-bit CPU reset circuit and power supply tips

More 8-bit computer: https://eater.net/8bit Check out Julian's channel: https://www.youtube.com/user/julius256 Support me on Patreon: https://www.patreon.com/beneater https://www.eater.net https://twitter.com/ben_eater https://www.patreon.com/beneater

Comments

Don Prefontaine

Ben, you are daisy-chaining your power connectors to each breadboard. If you use a scope of meter, you may find that the voltage at some of the furthest boards from the power source have dropped by as much as 0.5v. But then again, maybe the <a href="http://www.elegoo.com" rel="nofollow noopener" target="_blank">http://www.elegoo.com</a> breadboards I'm using are not the best quality. What seemed to work better for me was a separate power connector from the primary power attachment breadboard to every other breadboard; try to only daisy-chain from the north power rail of a breadboard to the south power rail of the same breadboad. I hope this helps. Another interesting consideration is if ppl are having inconsistent signaling issues, have them set their scopes to about 50ms/division and AC-couple the noise component. What you'll notice is that the Apple power supplies (1.0A and 2.4A) are considerably cleaner than everyone else's. I have tried Duracell, Jabra, Chinese clones of Apple, etc. Some of them had 450mv of very high frequency noise running on top of the DC clock signal.

Rob Bruno

I have a Samsung 2A power supply (also used an Apple 2.1A w/ no difference) and the power looks good. I have approx 5.1v at all points I have tested. I did however fully connect all power rails of the (genuine) BB830 breadboards. I connected the vertical rails on the right and left sides. I also connected the horizontal rails across the middle for each breadboard. Then I added some decoupling capacitors. I have a 0.01uF (ceramic )and a 2.2uF (electrolytic) on each of the 7 breadboards on the left and the same for the right. Hope this helps.

stuart martin

Electronics newbie here, but I originally built the entire computer using non-BPS breadboards and encountered a lot of interference of the clock signal, causing many spurious triggerings of the program counter and microinstruction counters. Presuming that my problem was due to stray inductance (or other) from the non-recommended breadboards, I bit the bullet and bought a replacement set of BPS breadboards. They didn't have the white ones , so I went for the transparent ones (which are otherwise identical, according to the datasheets). After rebuilding the entire left hand side of the computer, I moved to the program counter and BOOM, exactly the same behaviour of spurious triggerings due to a noisy signal on the clock pulse. Then I did some research and learned more about bypass /decoupling capacitors (mentioned very briefly by Ben in the clock episodes, and above). Placing a 103/0.01uF capacitor directly across the vss/gnd pins of the 74ls161s of the program counter and microinstruction counters cleaned up my noisy clock signals *perfectly* and I've not had a problem with them since. I now have almost no hair left, but this may save someone else from similar damage. Final comment for Ben: thank you so, so, so much for your amazing and inspiring videos. Rarely have I encountered such a natural educator.