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allisonaparrish@friend.camp
Oct 14, 2026, 5:04 PM
context: i found a board in the trash with an MC68HC001 processor on it. i wanna build a little computer with it, for laughs. the board itself (a 90s video compositor?) is kind of trashed, so i'm not all that eager to spend a lot of time figuring out how fix it.
question: is there a way to see if the processor is functional *without* having "the rest of the computer" (e.g. no RAM/ROM/serial)? if i just hook up VCC, GND and a clock source, will I see bus activity?
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Replies

allisonaparrish@friend.camp
Oct 14, 2026, 5:07 PM
(i haven't been able to find a document/tutorial that is like "so you have a 68k processor, here's how to build a computer around it" BUT i've looked at various little homebrews like https://github.com/74hc595/68k-nano so i know it's possible. i just don't want to go to the trouble of putting together a whole prototype only to discover that the processor is cooked)
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William D. Jonescr1901@mastodon.social
Oct 14, 2026, 5:20 PM
@aparrish The 68000 Microprocessor: Hardware and Software Principles and Applications by James L. Antonakos has a chapter on making a minimal 68k system from parts (Chapter 11). Unfortunately, I'm not sure my physical copy ("free to a good home" from a professor at Uni some 15 years ago) helps you :D.
I have the 4th edition.
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Your weary 'net denizencstanhope@social.coop
Oct 14, 2026, 5:22 PM
@aparrish There's a description of the reset process here. There should be some bus activity to look for:
https://archive.org/details/mc68000userman9thedmotorolaindextext/page/5-28/mode/2up?q=reset
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Joe Groffjoe
Oct 14, 2026, 5:14 PM
@aparrish if you can fashion an adapter to the 68000's DIN form factor, maybe you could try dropping it into an Amiga or Macintosh board, if you have one lying around?
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allisonaparrish@friend.camp
Oct 14, 2026, 5:15 PM
@joe i do not have such a board lying around, alas
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Joe Groffjoe
Oct 14, 2026, 5:20 PM
@aparrish if you have a scope or logic analyzer, one smoke test thing you can do with 68K processors, since `0000` is a nop, you could try tying the data bus lines to ground and watching the address lines, you should see the address bus count binary upward as it executes an endless series of nops
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Techokamitechokami@woof.tech
Oct 14, 2026, 5:48 PM
@joe @aparrish seconding this, it's pretty simple to breadboard as well. If you have some LEDs handy you can use them to monitor the address bus, and if you see it counting up in binary, you should be good
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Joe Groffjoe
Oct 14, 2026, 5:51 PM
@techokami @aparrish yeah that's a good point, you should be able to eyeball the higher bits of the address bus without needing a scope!
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linear cannonlinear@nya.social
Oct 14, 2026, 5:19 PM
@aparrish@friend.camp yes. this is called "free running" the cpu https://www.bigmessowires.com/2014/10/29/68k-free-run/
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allisonaparrish@friend.camp
Oct 14, 2026, 5:22 PM
@linear oh dang perfect! i didn't know "free run" was common terminology for this
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