Originally Posted by
JumpingJack
There is no such thing as an 'RC-wire', Hans means RC wire delay. Chips are wired up by etching or depositing metal lines within a dielectric material that is electrically isolating. Wires themselves have an intrinsic resistance and, also run parallel or one above another, due to the proximity two separate conductors separated in space setup a capacitance.
The result is a complicated RC circuit, where the capacitor/resistor have an intrinsic charge time. The effect is to delay propegation of signals through the matrix but some fundamental frequency or time delay. The time constant (tc) is proportional to the capacitance and resistance of that arrangement. tc=R*C (R=resistance and C = capacitance). The concept of RC delay in an RC circuit is taught in most freshman level physics courses when they study electricity and magnitism.
The industry must work to minimize this effect because a) it causes latency in signal propogation, b) works to limit clock speed, and c) increases power dissipation. This is why there was a move to copper lines 8-10 years ago, and this is why you hear all the hubbub about low-k and ultra-low k material (not to be confused with high-K for gates). To decrease the time constant you want low R and low C, copper has lower R per unit lenth than does aluminum (which was used prior ot copper). Capacitance gets lower with lower k (dielectric constant) material.
Jack
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