Smart routing can help reduce travel time and heat production, but a dramatic speed increase might require a change to the laws of physics. The smaller the wires, the greater the impedance and lower the current. As transistors shrink, so do the wires connecting them. Today, the wires connecting the transistors are a big part of the equation as well. Transistor speed also isn’t the only factor in clock speed anymore. While different transistor materials can allow for faster gate operation, the easy speed increases we once had are probably gone. Yet since Intel’s 45nm process, the transistor gate is approximately 0.9nm thick, or about the width of a single silicon atom. Typically, transistors have gotten faster because their gates (the part that moves in response to current) have thinned out. While transistors are reliably getting smaller (witness shrinking process sizes over time), they’re not operating more rapidly. Transistor design and composition are also preventing the easy headline clock speeds we once saw. Why CPU Clock Speed Isn’t Increasing: Transistor Troubles In the end, power requirements and heat production outpace clock speed increases. So as we try to increase clock speed, we find that heat and power consumption increase dramatically. Running those transistors and increasing clock speeds requires more voltage, leading to dramatically greater power consumption. So as clock speeds go up, more heat is generated, requiring more powerful cooling solutions. Increase in clock speeds also implies a voltage increase, which leads to a cubic increase in power consumption for the chip. The more transistors are added, the more robust the cooling system must be to accommodate the increased heat. That heat has to go somewhere, and proper cooling solutions and chip designs are required to maintain reasonable clock speeds. That heat is deadly to high-precision and high-speed silicon.
Cramming billions of transistors on a chip and turning them on and off thousands of times per second creates a ton of heat. Thermal losses are also a major factor in chip design.
Transistors shrink, but the power required to run them increases. Transistors have become so small that Dennard scaling no longer holds. However, we’ve begun to encounter the limits of Dennard scaling, and some are worried that Moore’s law is slowing down. This principle states that the power needed to run transistors in a particular unit volume stays constant even as the number of transistors increases. There’s also another factor at play, called Dennard scaling. Typically this means greater processing power. This means more transistors can be packed into a processor. Why CPU Clock Speed Isn’t Increasing: Heat and PowerĪs we know from Moore’s law, transistor size is shrinking on a regular basis.
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