DIY: 4bit computer

Read here.

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Back in 1999, I put that understanding to the ultimate test: I actually designed, and built, a simple but functional 4-bit computer from low-level electronic components (TTL logic gates.) Although this machine has less then one tenth of a percent of the speed and one millionth of the memory of a modern Pentium system, not to mention that its "user interface" is just a set of miniature switches and blinking LED lights, I still consider this a proud accomplishment.
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That is way cool! One of these things that I dream of doing before dying...
Way to go!