Reverse engineering old chips Ken Shirriff
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Gates get weird in the ALU<br />
+5<br />
Out<br />
4 5<br />
8<br />
7<br />
1 2 3 6<br />
The Z80 has a lot of very complex gates. Here’s one<br />
from the ALU with 9 transistors.<br />
If 1, 2, or 3 is on, the metal here is grounded.<br />
4 or 5 connect that to the output.<br />
6, 7, and 8 will also pull the output low.
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