Area counts silicon: cells times their sizes in library units of the teaching library. Power counts energy per second at stated activity. Timing counts delay against the clock, read as slack.
Slack is required time minus arrival time, in EXAMPLE nanoseconds. Positive slack meets the clock; negative slack misses it.
Axis | Tighter constraint looks like | Tool answer |
|---|---|---|
Timing | A shorter clock period. | Faster cells, more parallelism, duplicated logic. |
Area | A smaller cell budget. | Slower cells, shared resources, compact structures. |
Power | A lower milliwatt budget. | Gated clocks, calmer activity, high-Vt cells. |
A tighter clock usually grows area and power: the tool sizes gates up and duplicates cones to meet it. The exact cost varies between tools and libraries.
A tighter area bound usually slows the design and trims dynamic power: shared, smaller cells switch less capacitance but stretch delay.
Change | Area | Power | Timing |
|---|---|---|---|
Shorter clock target | Up: faster, larger cells. | Up: bigger gates switch more. | Better, at a cost. |
Smaller area budget | Down, by order. | Down for dynamic power. | Worse: slower, shared logic. |
Lower EXAMPLE voltage | May grow to recover speed. | Down quadratically. | Worse: gates slow down. |
Power and energy answer different questions. Power is joules per second; energy per operation divides power by the operation rate.
The calc block runs one EXAMPLE corner at two frequencies. Power doubles with frequency, but energy per cycle is unchanged.
EXAMPLE parameters (not real figures): alpha = 0.2, C = 50 pF, V = 0.9 V
at f = 1 GHz: P = 0.2 x 50e-12 x 0.81 x 1e9 = 0.0081 W = 8.1 mW
energy per cycle = 0.0081 / 1e9 = 8.1e-12 J = 8.1 pJ
at f = 2 GHz: P = 0.2 x 50e-12 x 0.81 x 2e9 = 0.0162 W = 16.2 mW
energy per cycle = 0.0162 / 2e9 = 8.1e-12 J = 8.1 pJ
power doubled, energy per operation is unchangedNo transform always helps: every speedup has an area or power price that varies with the design. Distrust any claim that a trick is free.
Larger, faster cells and duplicated logic. Timing was bought with area and power.
Neither. Both cost 8.1 pJ per cycle, so the energy per operation ties.