182: Digital Electronics: Microprocessor Speed And Clocks.
What are microprocessors and how have they changed? The first thing to understand is that a microprocessor by itself is useless. It can’t do anything without other components such as memory, communications, port controllers, display drivers, etc. All these are integrated circuits. There’re called integrated circuits, or ICs, because all the transistors are bundled together on a single piece of silicon that’s packaged inside a piece of plastic with connections exposed so it can connect with other ICs. The ICs are also sometimes called chips. Computers sometimes refer to a central processing unit or CPU. Think of a microprocessor as a CPU on a single integrated circuit. It still acts as the brains of the device and it coordinates the activities of all the other ICs. Probably the most critical component that a microprocessor relies on, other than a good supply of power anyway, is the clock. You’ve heard about computers running at some gigahertz speed or another. This is the clock speed. Computers didn’t always run this fast. Listen to the full episode for more information about clocks and how the microprocessor can read and write information from memory. Or you can also read the full transcript below. Transcript I’ve explained some of this in episodes 3 and 4 so make sure to listen to them for more information. This episode will help you understand the microprocessor from an electronic angle. The recent electronics episodes will also help. The first thing to understand is that a microprocessor by itself is useless. It can’t do anything without other components such as memory, communications, port controllers, display drivers, etc. All these are integrated circuits. There’re called integrated circuits, or ICs, because all the transistors are bundled together on a single piece of silicon that’s packaged inside a piece of plastic with connections exposed so it can connect with other ICs. The ICs are also sometimes called chips. I’ll explain transistors in another episode. I wanted to bring the focus back to programming for this episode so you don’t feel like this podcast has lost its direction. This is a programming podcast and learning about electronics will help you become a better programmer. Microprocessors used to have about 2 thousand transistors in the 1970’s and it’s gone up dramatically since then. The more transistors a processor has, the more it can do. Your smart phone has a microprocessor and it probably has 2 to 3 billion transistors. A high end graphics card also has a graphical processor and today might have as many as 15 billion transistors. Computers sometimes refer to a central processing unit or CPU. Think of a microprocessor as a CPU on a single integrated circuit. It still acts as the brains of the device and it coordinates the activities of all the other ICs. Probably the most critical component that a microprocessor relies on, other than a good supply of power anyway, is the clock. You’ve heard about computers running at some gigahertz speed. This is the clock speed. Computers didn’t always run this fast. The original IBM personal computers had a clock of 4 megahertz. And they had a turbo button that could increase the speed to 8 megahertz. A modern computer will likely have a clock speed of 2 to 3 gigahertz. A clock signal is nothing more than a voltage that goes from zero volts to whatever high voltage level your system is using and then back to zero volts, and then back to high. It does this very fast and regularly. The key to a good clean clock signal is that it should be regular. In other words, it shouldn’t remain high for some period of time and then low for a different period of time. And when it goes high again, it should remain high for the same length of time. Each time the clock signal goes high and then low and back to the same spot is called a cycle. And counting how many times each second it does th