You can try the first discovery and the 3D controls now. Stella unlocks every stage.
Datapath: One Instruction Journey
Start from an adder whose answer is wrong until it settles, then discover the clock tick that copies it into registers, an instruction that is just 32 bits, a five-beat journey through a town of blocks, a looping program, an overlapped pipeline, and the pull-back to the wafer.
WaferDieBlockWiringTransistorFinAtom
The beat that waits for the answer
In the previous chapter’s adder, the answer was wrong until the carry wave arrived. So a CPU puts registers — rows of boxes that hold numbers — after the logic, and copies the answer in only at the instant the clock ticks. Between ticks the logic settles, and only the settled answer is passed on. Speed up the clock and computation moves faster; go too fast, and the tick arrives before the wave does.
Speed up the clock and find the speed at which the values copied into the register start to go wrong.
- Length of one beat
- 1.00 ns
- How far light travels in one beat
- 30.0 cm
- 127 + 1 as copied into the register
- 128
- Copied after the answer settles
With this model’s slowest path, the limit is 4.0 GHz
You can try the first discovery and the 3D controls now. Stella unlocks every stage.