CPU Visual Handbook · lab

The datapath, running

Write a program on the right and the processor executes it in front of you — one instruction per clock. Solid lines carry data, dashed lines carry control. The thin ones settle inside the cycle; the thick ones cross the clock edge, and the dot travelling on them is the value waiting for the flank.

Nothing here is scripted. A box lights up because the ledger says it acted this tick, so a part that sits still is a part that did nothing. Slow the clock down and follow one value through.

The program also talks to the world, and it does so with no new instruction: storing to 0x1000 is speaking, loading from 0x1004 is listening to the dial. Two addresses that are not memory — which is how a small machine has always had a keyboard and a screen.