Accelerating Electronics: A Focus on Interconnects and Semiconductor Materials

When discussing the speed of electricity in electronic devices, we often think of it in two distinct areas: integrated circuits (IC) and interconnects. This article will delve into these areas, exploring how advancements in interconnect technology and semiconductor materials can impact the overall performance of electronic devices.

Understanding Interconnects

Interconnects, such as cables, play a crucial role in linking devices to CPU ICs. The main issue with these interconnections is not about how quickly electricity propagates through wires. Instead, the challenges lie in inductance capacity, cross-talk, and other interconnect-related factors. For instance, PCI Express 5.0 currently in wide use achieves a raw transfer speed of 32 GT/s, while PCI Express 6.0, with its speed of 64 GT/s, is still in the testing phase. Similarly, memory advancements, such as DDR5, achieve data transfer rates of 8 Gb/s per bit.

However, at these high speeds, the challenge lies in the buffers needed to drive the current through the wires. These buffers must be capable of overcoming the inductance and capacitance of the wires. This is a key area where technology is evolving, with optical interconnects from Intel achieving a throughput of 32 Gb/s over distances of 100 meters. Additionally, future plans include chiplet interconnects to enhance performance.

Physical Limitations Beyond Light Speed

It is important to note that physics limitations prevent us from going beyond the speed of light in materials. For instance, in glass fiber cables, the speed is about 70% of the speed in a vacuum. While using air as a conductor to increase light speed might seem like a solution, it comes with its own set of issues. In electronics, the speed of electricity is about 90% of the speed of light. However, wire inductance and capacitance can significantly impact signal propagation.

Speed of Electricity in Microcircuits

When we talk about the speed of electrons in microcircuits, the distances involved are minuscule, measured in micrometers, on the order of hundreds of microns. While the speed of electrons matters less, capacitance does become a significant issue. For example, turning a transistor on involves pushing charges into a capacitor, while turning it off requires discharging that capacitor. This process is influenced by the material used, with Silicon having lower electron mobility compared to Germanium or Gallium. To improve transistor speed, manufacturers might use Silicon as the base material and implement the transistor channel and gate with Germanium.

Node Size and Power Consumption

Smaller node sizes, such as 3nm, consume less power but tend to perform more slowly compared to larger transistors, such as Intel's 10nm nodes. Over time, manufacturers continuously work on improving operating clocks, but there are limitations. For instance, Intel's older 10nm node still achieves 6.5 GHz operating clocks, while TSMC's 5nm and lower nodes are limited to 5 GHz.

Evolution of CPU Architecture

The history of CPUs has shown that clock speeds alone are not the only determining factor for performance. Although maximum clock speeds are around 5 GHz, advancements in microarchitecture and the ability to execute multiple instructions in parallel have significantly enhanced processing power. Another approach has been the adoption of multicore CPUs. Even low-end smartphones often come with 2-4 cores, which greatly improves overall processing power without any significant changes in the physics of materials.